VCAA Mathematical Methods Calculus

15 sample questions with marking guides and sample answers · Avg. score: 58.5%

Q6
2023
QCAA
Paper 1
1 mark
Q6
1 mark

Substitutions for hh are used to estimate the limit of ah1h\frac{a^h - 1}{h} as h0h \to 0. Which sequence is the most appropriate?

A

4,2,1,0.5,0.25,0.125-4, -2, -1, -0.5, -0.25, -0.125 \dots

B

0.05,0.1,0.2,0.4,0.8-0.05, -0.1, -0.2, -0.4, -0.8 \dots

C

2,1,0,1,2,32, 1, 0, -1, -2, -3 \dots

D

1,2,3,4,5,61, 2, 3, 4, 5, 6 \dots

Reveal Answer
A

4,2,1,0.5,0.25,0.125-4, -2, -1, -0.5, -0.25, -0.125 \dots

Correct Answer

This sequence is appropriate because the magnitude of the values decreases (4,2,1,|-4|, |-2|, |-1|, \dots), meaning hh is getting progressively closer to 00.

B

0.05,0.1,0.2,0.4,0.8-0.05, -0.1, -0.2, -0.4, -0.8 \dots

This sequence is incorrect because the values are moving away from 00 (0.05,0.1,0.2,-0.05, -0.1, -0.2, \dots), which does not help estimate the limit as h0h \to 0.

C

2,1,0,1,2,32, 1, 0, -1, -2, -3 \dots

This sequence includes 00, where the expression ah1h\frac{a^h - 1}{h} is undefined (division by zero), and subsequent terms move away from 00.

D

1,2,3,4,5,61, 2, 3, 4, 5, 6 \dots

This sequence consists of increasing integers moving away from 00, which would be used to investigate the limit as hh \to \infty, not as h0h \to 0.

Q19
2020
QCAA
Paper 1
6 marks
Q19
6 marks

A horizontal point of inflection is a point of inflection that is also a stationary point.

Determine the value/s of kk for which the graph of f(x)=ln(x)kkxx+1f(x) = \frac{\ln(x)}{k} - \frac{kx}{x+1} has only one horizontal point of inflection.

Reveal Answer

f(x)=1kx(k(x+1)kx(x+1)2)f'(x) = \frac{1}{kx} - (\frac{k(x + 1) - kx}{(x + 1)^2})
Stationary points f(x)=0f'(x) = 0

0=1kx(k(x+1)kx(x+1)2)0 = \frac{1}{kx} - (\frac{k(x + 1) - kx}{(x + 1)^2})

0=1kxk(x+1)20 = \frac{1}{kx} - \frac{k}{(x + 1)^2}

0=x2+(2k2)x+10 = x^2 + (2 - k^2)x + 1 (i)

The quadratic has real roots when discriminant 0\ge 0

(2k2)240(2 - k^2)^2 - 4 \ge 0
2k2±22 - k^2 \ge \pm 2
There is only ONE phi \therefore
2k2=±22 - k^2 = \pm 2
k=0k = 0 (not valid)
and k2=4k^2 = 4 so
k=2,2k = 2, -2
Sub into (i) to determine the x-ordinate of the stationary point.
x=1\rightarrow x = 1
For k=2k = 2
f(x)=12x2+4(x+1)3\therefore f''(x) = \frac{-1}{2x^2} + \frac{4}{(x + 1)^3}
f(1)=12+48f''(1) = \frac{-1}{2} + \frac{4}{8}
f(1)=0f''(1) = 0
For k=2k = -2
f(x)=12x24(x+1)3f''(x) = \frac{1}{2x^2} - \frac{4}{(x + 1)^3}
f(1)=1248f''(1) = \frac{1}{2} - \frac{4}{8}
f(1)=0f''(1) = 0
For each kk value, x=1x = 1 is the x-ordinate of both a stationary point (f(x)=0f'(x) = 0) and a point of inflection (f(x)=0f''(x) = 0)
There is a point of horizontal inflection at x=1x = 1 when k=±2k = \pm 2

Marking Criteria
DescriptorMarks

correctly determines the first derivative

1

correctly determines the quadratic equation to identify the stationary point/s

1

determines valid and non-valid solutions of k

1

determines x-ordinate of stationary point

1

determines values of second derivative for both values of k

1

shows logical organisation communicating key steps

1
Q18
2022
VCAA
Paper 2
1 mark
Q18
1 mark

At the point where x=kx = k, the tangent to the circle given by the equation x2+(y1)2=1x^2 + (y - 1)^2 = 1 meets the positive direction of the xx-axis at an angle of 135135^\circ.
The value of kk could be

A

3-\sqrt{3}

B

1-1

C

12-\frac{1}{\sqrt{2}}

D

13-\frac{1}{\sqrt{3}}

E

0

Reveal Answer
A

3-\sqrt{3}

The circle's domain is 1x1-1 \le x \le 1, so x=3x = -\sqrt{3} is outside the circle and cannot be a point of tangency.

B

1-1

At x=1x = -1, the tangent line to the circle is vertical, meaning its slope is undefined rather than 1-1.

C

12-\frac{1}{\sqrt{2}}

Correct Answer

The tangent's slope is tan(135)=1\tan(135^\circ) = -1. Using implicit differentiation, y=xy1=1y' = -\frac{x}{y-1} = -1 gives y=x+1y = x + 1. Substituting this into the circle equation yields 2x2=12x^2 = 1, so x=±12x = \pm\frac{1}{\sqrt{2}}.

D

13-\frac{1}{\sqrt{3}}

This value would correspond to a different tangent slope, likely resulting from using an incorrect angle such as 120120^\circ or 150150^\circ.

E

0

At x=0x = 0, the tangent lines to the circle are horizontal (slope of 0), which corresponds to an angle of 00^\circ or 180180^\circ, not 135135^\circ.

Q20
2024
VCAA
Paper 2
1 mark
Q20
1 mark

Let f:RRf : R \rightarrow R, f(x)=x2(1x2)f(x) = x^2(1 - x^2) and g:[0,1]Rg : [0, 1] \rightarrow R, g(x)=f(xa)g(x) = f(x - a).
Find all real values of aa, such that g(0)g(0) is the absolute maximum value of gg.

A

a=±22a = \pm \frac{\sqrt{2}}{2}

B

a[22,22]a \in \left[-\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}\right]

C

a(,22][22,)a \in \left(-\infty, -\frac{\sqrt{2}}{2}\right] \cup \left[\frac{\sqrt{2}}{2}, \infty\right)

D

a[22,12][12,22]a \in \left[-\frac{\sqrt{2}}{2}, -\frac{1}{2}\right] \cup \left[\frac{1}{2}, \frac{\sqrt{2}}{2}\right]

E

a(,22][12,22]a \in \left(-\infty, -\frac{\sqrt{2}}{2}\right] \cup \left[\frac{1}{2}, \frac{\sqrt{2}}{2}\right]

Reveal Answer
A

a=±22a = \pm \frac{\sqrt{2}}{2}

This option only includes the points where g(0)g(0) reaches the global maximum of f(x)f(x), which is 14\frac{1}{4}. It misses the intervals where g(0)g(0) is a local maximum that remains the absolute maximum on the restricted interval [0,1][0, 1].

B

a[22,22]a \in \left[-\frac{\sqrt{2}}{2}, \frac{\sqrt{2}}{2}\right]

This incorrectly assumes aa can be any value between the critical points. For a(12,12)a \in \left(-\frac{1}{2}, \frac{1}{2}\right), the shifted interval [a,1a][-a, 1-a] will contain values of xx where f(x)>f(a)f(x) > f(-a), meaning g(0)g(0) is not the maximum.

C

a(,22][22,)a \in \left(-\infty, -\frac{\sqrt{2}}{2}\right] \cup \left[\frac{\sqrt{2}}{2}, \infty\right)

This option incorrectly includes a22a \ge \frac{\sqrt{2}}{2}. For these values, a22-a \le -\frac{\sqrt{2}}{2}, and the function f(x)f(x) is strictly increasing immediately to the right of a-a, so g(0)g(0) cannot be the maximum on [0,1][0, 1].

D

a[22,12][12,22]a \in \left[-\frac{\sqrt{2}}{2}, -\frac{1}{2}\right] \cup \left[\frac{1}{2}, \frac{\sqrt{2}}{2}\right]

This incorrectly includes a[22,12]a \in \left[-\frac{\sqrt{2}}{2}, -\frac{1}{2}\right]. For these negative values of aa, the function f(x)f(x) increases as xx moves to the right of a-a, meaning g(x)g(x) will exceed g(0)g(0) on the interval [0,1][0, 1].

E

a(,22][12,22]a \in \left(-\infty, -\frac{\sqrt{2}}{2}\right] \cup \left[\frac{1}{2}, \frac{\sqrt{2}}{2}\right]

Correct Answer

To make g(0)=f(a)g(0) = f(-a) the maximum on [a,1a][-a, 1-a], a-a must either be in the region where f(x)f(x) is strictly decreasing (a22    a22-a \ge \frac{\sqrt{2}}{2} \implies a \le -\frac{\sqrt{2}}{2}), or a-a must be on the decreasing slope [22,0][-\frac{\sqrt{2}}{2}, 0] such that the right endpoint doesn't exceed f(a)f(-a), requiring 1aa    a121-a \le a \implies a \ge \frac{1}{2}.

Q3
2024
QCAA
Paper 2
1 mark
Q3
1 mark

The derivative of the function f(x)f(x) is given by f(x)=sin(2x)f'(x) = \sin(2x). It is known that f(π2)=4f\left(\frac{\pi}{2}\right) = 4.
Determine f(x)f(x).

A

cos(2x)+3-\cos(2x) + 3

B

cos(2x)+5\cos(2x) + 5

C

12cos(2x)+3.5-\frac{1}{2}\cos(2x) + 3.5

D

12cos(2x)+4.5\frac{1}{2}\cos(2x) + 4.5

Reveal Answer
A

cos(2x)+3-\cos(2x) + 3

This option fails to apply the reverse chain rule (u-substitution). The integral of sin(kx)\sin(kx) is 1kcos(kx)-\frac{1}{k}\cos(kx), so you must divide by the coefficient 22.

B

cos(2x)+5\cos(2x) + 5

This option uses the wrong sign for the antiderivative and misses the chain rule factor. The integral of sin(x)\sin(x) is cos(x)-\cos(x), not cos(x)\cos(x), and the result must be divided by 22.

C

12cos(2x)+3.5-\frac{1}{2}\cos(2x) + 3.5

Correct Answer

Integrating f(x)=sin(2x)f'(x) = \sin(2x) yields f(x)=12cos(2x)+Cf(x) = -\frac{1}{2}\cos(2x) + C. Using the condition f(π2)=4f(\frac{\pi}{2}) = 4, we solve 4=12cos(π)+C4 = -\frac{1}{2}\cos(\pi) + C to find C=3.5C = 3.5.

D

12cos(2x)+4.5\frac{1}{2}\cos(2x) + 4.5

This option has the wrong sign for the cosine term. Since the derivative of cos(x)\cos(x) is sin(x)-\sin(x), the antiderivative of sin(x)\sin(x) must be negative.

Q11
2024
QCAA
Paper 2
4 marks
Q11
4 marks

State the trapezoidal rule and use it with six strips to determine an approximate value of the definite integral for the curve of f(x)=4(x3)2f(x) = 4(x-3)^2 from x=0x = 0 to x=3x = 3. Show all substitutions made into the rule.

Reveal Answer

w=banw=\dfrac{b-a}{n}

=306=\dfrac{3-0}{6}

=12=\dfrac{1}{2}

A12w[f(x0)+2f(x1)+2f(x2)++2f(xn)]A\approx \dfrac{1}{2}w\left[f(x_0)+2f(x_1)+2f(x_2)+\ldots+2f(x_n)\right]

=12×12[36+2×25+2×16+2×9+2×4+2×1+0]=\dfrac{1}{2}\times \dfrac{1}{2}\left[36+2\times 25+2\times 16+2\times 9+2\times 4+2\times 1+0\right]

=36.5 units2=36.5\ \text{units}^2

Marking Criteria
DescriptorMarks

Correctly determines the rectangle width

1

Correctly states the trapezoidal rule

1

Substitutes appropriate values into the trapezoidal rule

1

Determines the approximate value of the definite integral

1
Q2
2024
VCAA
Paper 2
1 mark
Q2
1 mark

A function g:RRg : R \rightarrow R has the derivative g(x)=x3xg'(x) = x^3 - x.

Given that g(0)=5g(0) = 5, the value of g(2)g(2) is

A

2

B

3

C

5

D

7

Reveal Answer
A

2

Incorrect. Evaluating the antiderivative g(x)=x44x22+5g(x) = \frac{x^4}{4} - \frac{x^2}{2} + 5 at x=2x=2 yields 7, not 2.

B

3

Incorrect. This might result from ignoring the constant of integration C=5C=5 and calculating g(2)=42=2g(2) = 4 - 2 = 2, then making an arithmetic error.

C

5

Incorrect. This is the value of the initial condition g(0)g(0), not the requested value g(2)g(2).

D

7

Correct Answer

Correct. Integrating g(x)g'(x) gives g(x)=x44x22+Cg(x) = \frac{x^4}{4} - \frac{x^2}{2} + C. Substituting g(0)=5g(0) = 5 gives C=5C = 5, and evaluating g(2)g(2) yields 16442+5=7\frac{16}{4} - \frac{4}{2} + 5 = 7.

Q14
2025
VCAA
Paper 2
1 mark
Q14
1 mark

Let ff be the probability density function for a continuous random variable XX, where

f(x)={ksin(x)0x<π4kcos(x)π4xπ20otherwisef(x) = \begin{cases} k\sin(x) & 0 \le x < \frac{\pi}{4} \\ k\cos(x) & \frac{\pi}{4} \le x \le \frac{\pi}{2} \\ 0 & \text{otherwise} \end{cases}

and kk is a positive real number.

The value of kk is

A

12\frac{1}{\sqrt{2}}

B

122\frac{1}{2 - \sqrt{2}}

C

2+2\sqrt{2} + 2

D

222 - \sqrt{2}

Reveal Answer
A

12\frac{1}{\sqrt{2}}

Incorrect. This value does not make the total area under the probability density function equal to 1, likely resulting from an error in evaluating the trigonometric integrals.

B

122\frac{1}{2 - \sqrt{2}}

Correct Answer

Correct. For f(x)f(x) to be a valid probability density function, its integral over all xx must equal 1. Evaluating 0π/4ksin(x)dx+π/4π/2kcos(x)dx=1\int_0^{\pi/4} k\sin(x)dx + \int_{\pi/4}^{\pi/2} k\cos(x)dx = 1 yields k(22)=1k(2 - \sqrt{2}) = 1, which gives k=122k = \frac{1}{2 - \sqrt{2}}.

C

2+2\sqrt{2} + 2

Incorrect. This might result from incorrectly rationalizing the denominator or making an arithmetic error when solving k(22)=1k(2 - \sqrt{2}) = 1.

D

222 - \sqrt{2}

Incorrect. This is the value of the integral when k=1k=1. Since the total area must be 1, kk must be the reciprocal of this value.

Q17
2024
QCAA
Paper 1
3 marks
Q17
3 marks

A community group that uses social media created a new post on the internet on a day when they had 1000 members. The rate of change in their number of members (members/day) is given by f(t)=3e0.5tf'(t) = 3e^{0.5t}, where tt represents days after the new post.
Determine the time it will take for the community group to achieve seven times the initial number of members. Express your answer in the form aln(b)a \ln(b).

Reveal Answer

7 times the members is 7000.
Let m be the time when 7000 members is reached.
The required change in members is 6000.
6000=0m3e0.5tdt6000 = \int_0^m 3e^{0.5t} dt
=[3×10.5e0.5t]0m= \left[ 3 \times \frac{1}{0.5}e^{0.5t} \right]_0^m
=[6e0.5t]0m= \left[ 6e^{0.5t} \right]_0^m
=[6e0.5m6e0]= \left[ 6e^{0.5m} - 6e^0 \right]
=[6e0.5m6]= \left[ 6e^{0.5m} - 6 \right]
6000=6e0.5m66000 = 6e^{0.5m} - 6
6006=6e0.5m6006 = 6e^{0.5m}
60066=e0.5m\frac{6006}{6} = e^{0.5m}
0.5m=ln10010.5m = \ln 1001
m=2ln1001 daysm = 2\ln 1001 \text{ days}

Marking Criteria
DescriptorMarks

Correctly uses the initial conditions to determine the increase

1

Correctly determines the integral

1

Determines the number of days required

1
Q3
2022
VCAA
Paper 2
1 mark
Q3
1 mark

The gradient of the graph of y=e3xy = e^{3x} at the point where the graph crosses the vertical axis is equal to

A

00

B

1e\frac{1}{e}

C

11

D

ee

E

33

Reveal Answer
A

00

Incorrect. This might result from confusing the x-coordinate of the y-intercept (x=0x=0) with the gradient itself.

B

1e\frac{1}{e}

Incorrect. This value does not match the derivative evaluated at the y-intercept.

C

11

Incorrect. This is the y-coordinate of the y-intercept (y=e0=1y=e^0=1), not the gradient. It could also result from forgetting the chain rule and incorrectly assuming the derivative is e3xe^{3x}.

D

ee

Incorrect. This value does not correspond to the derivative evaluated at x=0x=0.

E

33

Correct Answer

Correct. The gradient is found using the derivative dydx=3e3x\frac{dy}{dx} = 3e^{3x}. The graph crosses the vertical axis at x=0x=0, so evaluating the derivative gives 3e3(0)=33e^{3(0)} = 3.

Q8
2023
QCAA
Paper 2
1 mark
Q8
1 mark

The number of koalas in a conservation park is modelled by N=15ln(7t+1)N = 15 \ln(7t + 1), t1t \geq 1, where tt represents the time (years) since the park opened. There were 20 koalas in the park when it opened.

Determine the approximate rate of change in the number of koalas when t=3t = 3.

A

46

B

26

C

25

D

5

Reveal Answer
A

46

This is the value of the function N(3)=15ln(22)46N(3) = 15 \ln(22) \approx 46. This represents the number of koalas (or the population increase) at year 3, rather than the rate at which the population is changing.

B

26

This value appears to be the result of calculating N(3)2026N(3) - 20 \approx 26. This subtracts the initial population from the model's value at t=3t=3, which does not represent the instantaneous rate of change.

C

25

This is an incorrect value. It does not correspond to the derivative at t=3t=3 or the function value, likely resulting from a calculation error.

D

5

Correct Answer

The rate of change is found by taking the derivative dNdt\frac{dN}{dt}. Using the chain rule, dNdt=1517t+17=1057t+1\frac{dN}{dt} = 15 \cdot \frac{1}{7t+1} \cdot 7 = \frac{105}{7t+1}. Evaluating at t=3t=3 gives 105224.77\frac{105}{22} \approx 4.77, which rounds to 5.

Q15
2022
QCAA
Paper 1
4 marks
Q15
4 marks

The derivative of a function is given by f(x)=ex(x4)f'(x) = e^x(x-4).
Determine the interval on which the graph of f(x)f(x) is both decreasing and concave up.

Reveal Answer

The function is decreasing when f(x)<0f'(x) < 0 and concave up when f(x)>0f''(x) > 0
f(x)=(x4)ex<0f'(x) = (x-4)e^x < 0 when x<4x < 4

f(x)=(x4)ex+ex=ex(x3)>0f''(x) = (x-4)e^x + e^x = e^x(x-3) > 0 when x>3x > 3

Therefore, the function is decreasing and concave up when 3<x<43 < x < 4

Marking Criteria
DescriptorMarks

correctly describes conditions when the function is decreasing and concave up

1

correctly determines the interval where f(x) is decreasing

1

correctly determines the interval where f(x) is concave up

1

determines interval when function is decreasing and concave up

1
Q4
2021
VCAA
Paper 2
1 mark
Q4
1 mark

The maximum value of the function h:[0,2]R,h(x)=(x2)exh : [0, 2] \rightarrow R, h(x) = (x - 2)e^x is

A

e-e

B

0

C

1

D

2

E

ee

Reveal Answer
A

e-e

This is the minimum value of the function on the interval, which occurs at the critical point x=1x = 1 since h(1)=eh(1) = -e.

B

0

Correct Answer

To find the maximum, we evaluate h(x)h(x) at the critical point x=1x=1 and endpoints x=0,2x=0, 2. Comparing h(0)=2h(0) = -2, h(1)=eh(1) = -e, and h(2)=0h(2) = 0, the maximum value is 00.

C

1

This is the xx-value of the critical point (found by setting h(x)=(x1)ex=0h'(x) = (x-1)e^x = 0), not the maximum value of the function itself.

D

2

This is the xx-value at which the maximum occurs, but the question asks for the maximum value of the function, which is h(2)=0h(2) = 0.

E

ee

This value does not correspond to the function evaluated at any critical point or endpoint within the given interval [0,2][0, 2].

Q1
2025
QCAA
Paper 2
1 mark
Q1
1 mark

Determine 10.4x3dx\int 10.4x^3 \, dx

A

2.6x4+c2.6x^4 + c

B

6.4x4+c6.4x^4 + c

C

14.4x4+c14.4x^4 + c

D

41.6x4+c41.6x^4 + c

Reveal Answer
A

2.6x4+c2.6x^4 + c

Correct Answer

Correct. Using the power rule for integration, we increase the exponent by 1 and divide the coefficient by the new exponent: 10.43+1x3+1+c=2.6x4+c\frac{10.4}{3+1}x^{3+1} + c = 2.6x^4 + c.

B

6.4x4+c6.4x^4 + c

Incorrect. This option incorrectly subtracts the new exponent (4) from the coefficient 10.4 instead of dividing by it.

C

14.4x4+c14.4x^4 + c

Incorrect. This option incorrectly adds the new exponent (4) to the coefficient 10.4 instead of dividing by it.

D

41.6x4+c41.6x^4 + c

Incorrect. This option incorrectly multiplies the coefficient 10.4 by the new exponent (4) instead of dividing by it, confusing the integration rule with the differentiation rule.

Q14
2022
QCAA
Paper 1
6 marks
Q14

The rate that water fills an empty vessel is given by dVdt=0.25e0.25t\frac{dV}{dt} = 0.25e^{0.25t} (in litres per hour), 0t8ln(6)0 \le t \le 8\ln(6), where tt is time (in hours).

Q14a
2 marks

Determine the function that represents the volume of water in the vessel (in litres).

Reveal Answer

V=0.25e0.25tdtV = \int 0.25e^{0.25t} dt
=e0.25t+c= e^{0.25t} + c
when t=0,V=0t = 0, V = 0
0=e0.25×0+c\therefore 0 = e^{0.25 \times 0} + c
c=1\therefore c = -1
V=e0.25t1\therefore V = e^{0.25t} - 1

Marking Criteria
DescriptorMarks

correctly determines the integral of the function V(t)

1

determines the value of c

1
Q14b
2 marks

The vessel is full when t=8ln(6)t = 8\ln(6). Determine the volume of water, to the nearest litre, the vessel can hold when full.

Reveal Answer

V(8ln(6))=e0.25×8ln(6)1V(8\ln(6)) = e^{0.25 \times 8 \ln(6)} - 1
=361= 36 - 1

=35= 35 litres

Marking Criteria
DescriptorMarks

determines the simplified exponential term

1

determines number of litres

1
Q14c
2 marks

Use information from the table and the trapezoidal rule to determine the approximate volume of water in the vessel after three hours.

ttdVdt\frac{dV}{dt}
00.25
10.32
20.41
30.53
Reveal Answer

Using trapezoidal rule
Volume after 3 hours =12(0.25+0.53+2(0.32+0.41))= \frac{1}{2}(0.25+0.53+2(0.32+0.41))

Volume after 3 hours =1.12= 1.12 litres

Marking Criteria
DescriptorMarks

establishes expression for approximate number of litres of water in vessel after 3 hours

1

determines approximate number of litres

1

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