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VCE 11 Methods 2023

10.02 Tangents and their equations

Worksheet
Equation of a tangent from a graph
1

Each of the following graphs contain a curve, f \left( x \right), along with one of its tangents, g \left( x \right).

i

State the coordinates of the point at which g \left( x \right) is a tangent to the curve f \left( x \right).

ii

State the gradient of the tangent.

iii

Hence determine the equation of the line y = g \left( x \right).

a
-4
-3
-2
-1
1
2
3
4
x
-4
-3
-2
-1
1
2
3
4
y
b
-3
-2
-1
1
2
3
x
-6
-5
-4
-3
-2
-1
1
2
3
y
c
1
2
3
4
5
x
-1
1
2
3
y
d
1
2
3
4
5
x
-3
-2
-1
1
2
y
e
-1
1
2
3
4
5
x
1
2
3
4
5
y
2

Each of the following graphs contain a curve, f \left( x \right), along with one of its tangents, g \left( x \right).

i

State the coordinates of the point at which g \left( x \right) is a tangent to the curve f \left( x \right).

ii

State the gradient of the tangent.

iii

Hence determine the equation of the line y = g \left( x \right).

iv

State the x-coordinate of the point on the curve at which we could draw a tangent that has the same gradient as g \left( x \right).

a
-2
-1
1
2
3
x
-6
-5
-4
-3
-2
-1
1
2
3
y
b
-3
-2
-1
1
2
x
-4
-3
-2
-1
1
2
3
4
5
y
3

Consider the graph of the function f \left( x \right):

a

Sketch the graph of the function \\ g \left( x \right) = 2 x + 3 on the same number plane.

b

Is g \left( x \right) a tangent to f \left( x \right)? Explain your answer.

-4
-3
-2
-1
1
2
3
4
x
1
2
3
4
5
6
7
8
9
y
4

Consider the graph of the function f \left( x \right):

a

Sketch the graph of the function \\ g \left( x \right) = 2 x-1 on the same number plane.

b

Is g \left( x \right) a tangent to f \left( x \right)? Explain your answer.

-4
-3
-2
-1
1
2
3
4
x
-4
-3
-2
-1
1
2
3
4
y
5

Consider the graph of the function f \left( x \right):

a

Sketch the graph of the function \\ g \left( x \right) = 3 x + 3 on the same number plane.

b

Is g \left( x \right) a tangent to f \left( x \right)? Explain your answer.

-4
-3
-2
-1
1
2
3
4
x
-4
-3
-2
-1
1
2
3
4
5
y
6

Consider the graph of the function f \left( x \right):

a

Sketch the graph of the function \\ g \left( x \right) = 4 x + 7 on the same number plane.

b

Is g \left( x \right) a tangent to f \left( x \right)? Explain your answer.

-4
-3
-2
-1
1
2
x
-8
-6
-4
-2
2
4
6
8
y
7

Consider the curve given by the function f \left( x \right) = x^{2} - 1.

a

Find the gradient of the tangent to the curve at the point \left(1, 0\right).

b

Graph the curve and the tangent at the point \left(1, 0\right) on a number plane.

8

Consider the curve given by the function f \left( x \right) = x^{2} - 4 x + 2.

a

Find the gradient of the tangent to the curve at the point \left(3, -1\right).

b

State the coordinates of the vertex of the parabola f \left( x \right) = x^{2} - 4 x + 2.

c

Graph the curve and the tangent at the point \left(3, -1\right) on a number plane.

Equation of a tangent at a given point
9

Consider the curve given by the function f \left( x \right) = x^{3} + 5 x.

Find the gradient of the tangent at the point \left(2, 18\right).

10

Consider the parabola f \left( x \right) = x^{2} + 3 x - 10.

a

Find the x-intercepts.

b

Find the gradient of the tangent at the positive x-intercept.

11

Consider the function y = x^{2} - 3 x + 4. State the x-coordinate of the point on the curve where the tangent makes an angle of 45 \degree with the x-axis.

12

Given that y = \dfrac{1}{3} x^{3} + \dfrac{1}{6} x^{6} + 2 x:

a

Find \dfrac{dy}{dx}.

b

Evaluate \dfrac{dy}{dx} when x = - 7.

13

Consider the tangent to the curve f \left( x \right) = x^{2} at the point \left( - 1 , 1\right).

a

Find the gradient of the function f \left( x \right) = x^{2} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = x^{2} at the point \left( - 1 , 1\right).

14

Consider the tangent to the curve f \left( x \right) = x^{3} at the point \left( - 1 , -1\right).

a

Find the gradient of the function f \left( x \right) = x^{3} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = x^{3} at the point \left( - 1 , -1\right).

15

Consider the tangent to the curve f \left( x \right) = - x^{2} at the point \left( - 3 , - 9 \right).

a

Find the gradient of the function f \left( x \right) = - x^{2} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = - x^{2} at the point \left( - 3 , - 9 \right).

16

Consider the tangent to the curve f \left( x \right) = - x^{3} at the point \left(2, - 8 \right).

a

Find the gradient of the function f \left( x \right) = - x^{3} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = - x^{3} at the point \left(2, - 8 \right).

17

Consider the tangent to the curve f \left( x \right) = x^{2} at the point \left( - 2 , 4\right).

a

Find the gradient of the function f \left( x \right) = x^{2} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = x^{2} at the point \left( - 2 , 4\right)

18

Consider the tangent to the curve f \left( x \right) = 6 \sqrt{x} at the point \left(4, 12\right).

a

Find the gradient of the function f \left( x \right) = 6 \sqrt{x} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = 6 \sqrt{x} at the point \left(4, 12\right).

19

Consider the tangent to the curve f \left( x \right) = 5 \sqrt{x} at the point \left(\dfrac{1}{9}, \dfrac{5}{3}\right).

a

Find the gradient of the function f \left( x \right) = 5 \sqrt{x} at this point.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = 5 \sqrt{x} at the point \left(\dfrac{1}{9}, \dfrac{5}{3}\right).

20

Find the equation of the tangent of the following curves at the given point:

a
f \left( x \right) = \left( 3 x - 1\right) \left( 2 x - 5\right), at the point \left(2, - 5 \right)
b
f \left( x \right) = x^{2} + x, at the point \left(2, 6\right)
c
f \left( x \right) = x - \dfrac{16}{x}, at the point \left(2, - 6 \right)
d
f \left( x \right) = - \dfrac{27}{x^{2}}, at the point \left(3, - 3 \right)
e
f \left( x \right) = - 3 x^{2} at the point \left(3, - 27 \right)
21

Consider the tangent to the curve f \left( x \right) = 3 x^{3} at x = 2.

a

Describe what must be done to find the equation of the tangent to the curve f(x) at \\ x=2.

b

Hence, find the equation of the tangent to the curve f \left( x \right) = 3 x^{3} at x = 2.

22

Consider the tangent to the curve f \left( x \right) = \dfrac{2}{x^{3}} at x = - 2.

a

Find the gradient of the function f \left( x \right) = \dfrac{2}{x^{3}} at x = - 2.

b

Find the y-coordinate of the point on the curve where x=-2.

c

Hence, find the equation of the tangent to the curve f \left( x \right) = \dfrac{2}{x^{3}} at x = - 2.

23

Consider the function f \left( x \right) = 3 x^{2}.

a

Find the gradient of the function at x = 2

b

Find the y-coordinate of the point on the function at x=2.

c

Hence, find the equation of the tangent to the curve f \left( x \right) = 3 x^{2} at x = 2.

24

Consider the tangent to the curve f \left( x \right) = - 2 x^{2} + 8 x + 2 at x = 1.

a

Find the y-coordinate of the point of intersection between the tangent and the curve.

b

Hence, determine the equation of the tangent to the curve f \left( x \right) = - 2 x^{2} + 8 x + 2 at \\ x = 1.

25

Find the equation of the tangent to the curve f \left( x \right) = 0.3 x^{3} - 5 x^{2} - x + 4 at x = 1.

26

Find the equation of the tangent to the curve f \left( x \right) = \dfrac{9 x + 4}{3 x} at x = - 1.

27

Find the equation of the tangent to the curve g \left( x \right) = \dfrac{8 x^{7} - 6 x^{6} + 4 x^{5} + 7}{2 x^{2}} at x = 1.

28

From an external point \left(3, 2\right), two tangents are drawn to the curve y = x^{2} - 6.

a

Find the gradient of both tangents.

b

Find the equation of both tangents.

29

Find the equation of the tangent to the parabola y = 2 x^{2} + 8 x - 5 at the point where the gradient is 0.

30

Consider the curve y = x^{3} - x^{2} and the line 4 x - y = 11.

a

Find the x-coordinates of the points on the curve at which the tangents are perpendicular to the line 4 x - y = 11.

b

Find the equation of the tangent to the curve y = x^{3} - x^{2} at each of these \\ x-coordinates.

Applications
31

For each of the following:

i

Find the x-coordinate of point M.

ii

Find the y-coordinate of point M.

a

At point M\left(x, y\right), the equation of the tangent to the curve y = x^{2} is given by y = 4 x - 4.

b

At point M\left(x, y\right), the equation of the tangent to the curve y = x^{3} is given by \\ y = 12 x - 16.

32

Consider the function f \left( x \right) = \dfrac{4 x^{3}}{3} + \dfrac{5 x^{2}}{2} - 3 x + 7. Find the x-coordinates of the points on the curve whose tangent is parallel to the line y = 3 x + 7.

33

5 x + y + 2 = 0 is the tangent to the curve y = x^{2} + b x + c at the point \left(9, - 47 \right).

a

Find the derivative \dfrac{d y}{d x} of y = x^{2} + b x + c.

b

Find the gradient of the tangent to the curve at x = 9.

c

Solve for the value of b.

d

Solve for the value of c.

34

Consider the function f \left( x \right) = x^{2} + 5 x.

a

Find the x-coordinate of the point at which f \left( x \right) has a gradient of 13.

b

Hence, state the coordinates of the point on the curve where the gradient is 13.

35

Consider the function f \left( x \right) = x^{3} - 6 x^{2}.

a

Find the x-coordinates of the points at which f \left( x \right) has a gradient of 495.

b

Hence, state the coordinates of the points on the curve where the gradient is 495.

36

Consider the function f \left( x \right) = x^{3} + 3 x^{2} - 19 x + 2.

a

Find the x-coordinates of the points at which f \left( x \right) has a gradient of 5.

b

Hence, state the coordinates of the points on the curve where the gradient is 5.

37

Consider the function f \left( x \right) = x^{3} + 6 x^{2} - 14 x - 2.

a

Find the x-coordinates of the points on the curve where the gradient is the same as that of g \left( x \right) = 22 x - 4.

b

Hence, state the coordinates of the points on the curve where the gradient is the same as that of g \left( x \right) = 22 x - 4.

38

The curve f \left( x \right) = k \sqrt{x} - 5 x has a gradient of 0 at x = 16.Find the value of k.

39

Consider the function y = 4 x^{2} - 5 x + 2.

a

Find \dfrac{dy}{dx}.

b

Hence, find the value of x at which the tangent to the parabola is parallel to the x-axis.

40

Consider the function f \left( x \right) = 5 x^{2} + \dfrac{4}{x} - 1. The tangent to the curve at the point \left(2, 21\right) makes an angle of \theta with the x-axis. Find \theta, correct to the nearest degree.

41

The curve y = a x^{3} + b x^{2} + 2 x - 17 has a gradient of 58 at the point \left(2, 31\right). Find the values of a and b.

42

The graph of y = a x^{3} + b x^{2} + c x + d intersects the x-axis at \left(2, 0\right), where it has a gradient of 36. It also intersects the y-axis at y = - 28, where the tangent is parallel to the x-axis.

Find the values of a, b, c and d.

43

In the following graph, the line y = \dfrac{x}{10} + b is a tangent to the graph of f \left( x \right) = 6 \sqrt{x} at x = a.

a

Find the value of a.

b

Find the value of b.

x
y
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Outcomes

U1.AoS3.3

use of gradient of a tangent at a point on the graph of a function to describe and measure instantaneous rate of change of the function, including consideration of where the rate of change is positive, negative or zero, and the relationship of the gradient function to features of the graph of the original function.

U1.AoS3.5

use graphical, numerical and algebraic approaches to find an approximate value or the exact value (as appropriate) for the gradient of a secant or tangent to a curve at a given point

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