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VCE 11 Methods 2023

2.06 Key features of quadratic functions

Worksheet
Key features of parabolas
1

Consider the general quadratic equation y = a x^{2} + b x + c, a \neq 0.

a

If a \lt 0, in what direction will the parabola open?

b

If a \gt 0, in what direction will the parabola open?

2

Does the parabola represented by the equation y = x^{2} - 8 x + 9 open upward or downward?

3

Does the graph of y = x^{2} + 6 have any x-intercepts? Explain your answer.

4

State whether the following parabolas have x-intercepts:

a
y = \left(x - 7\right)^{2} + 4
b
y = - \left(x - 7\right)^{2} + 4
c
y = - \left(x - 7\right)^{2} - 4
d
y = \left(x - 7\right)^{2} - 4
5

Consider the given graph:

a

What are the x-intercepts?

b

What is the y-intercept?

c

What is the maximum value?

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

Consider the given graph:

a

Is the curve concave up or concave down?

b

State the y-intercept of the graph.

c

What is the minimum value?

d

At which value of x does the minimum value occur?

e

Determine the interval of x for which the graph is decreasing.

-5
-4
-3
-2
-1
1
x
-1
1
2
3
4
5
6
7
8
9
10
y
7

Consider the graph of the parabola:

a

State the coordinates of the x-intercept.

b

State the coordinates of the vertex.

c

State whether the following statements are true about the vertex:

i

The vertex is the minimum value of the graph.

ii

The vertex occurs at the x-intercept.

iii

The vertex lies on the axis of symmetry.

iv

The vertex is the maximum value of the graph.

-5
-4
-3
-2
-1
1
2
3
x
-12
-10
-8
-6
-4
-2
y
8

Suppose that a particular parabola is concave down, and its vertex is located in quadrant 2.

a

How many x-intercepts will the parabola have?

b

How many y-intercepts will the parabola have?

9

Suppose that a particular parabola has two x-intercepts, and its vertex is located in quadrant 4. Will such a parabola be concave up or concave down?

10

Consider the quadratic function defined in the table on the right:

a

What are the coordinates of the vertex?

b

What is the minimum value of the function?

xy
-711
-66
-53
-42
-33
-26
-111
11

A vertical parabola has an x-intercept at \left(-1, 0\right) and a vertex at \left(1, - 6 \right). Find the other \\x-intercept.

12

State whether the following can be found, without any calculation, from the equation of the form y = \left(x - h\right)^{2} + k but not from the equation of the form y = x^{2} + b x + c:

a

x-intercepts

b

y-intercept

c

vertex

13

Quadratic function A is represented graphically as shown. Quadratic function B, which is concave down, shares the same x-intercepts as quadratic function A, but has a y-intercept closer to the origin. Which of the functions has a greater maximum value?

-4
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-1
1
2
3
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x
-8
-6
-4
-2
2
4
6
8
10
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y
14

What is the axis of symmetry of the parabola y = k \left(x - 7\right) \left(x + 7\right) for any value of k?

15

Consider the equation y = 25 - \left(x + 2\right)^{2}. What is the maximum value of y?

16

Consider the function y = \left(14 - x\right) \left(x - 6\right).

a

State the zeros of the function.

b

Find the axis of symmetry.

c

Is the graph of the function concave up or concave down?

d

Determine the maximum y-value of the function.

17

Consider the parabola of the form y = a x^{2} + b x + c, where a \neq 0.

Complete the following statement:

The x-coordinate of the vertex of the parabola occurs at x = ⬚. The y-coordinate of the vertex is found by substituting x = ⬚ into the parabola's equation and evaluating the function at this value of x.

18

Find the x-coordinate of the vertex of the parabola represented by P \left( x \right) = p x^{2} - \dfrac{1}{2} p x - q.

19

Consider the graph of the function

f \left( x \right) = - x^{2} - x + 6:

Using the graph, write down the solutions to the equation - x^{2} - x + 6 = 0.

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-1
1
2
3
4
x
-5
-4
-3
-2
-1
1
2
3
4
5
6
7
y
20

True or false:

a

The quadratic formula can be used to find the y-intercept.

b

If the parabola has only one x-intercept , then the x-intercept is also the vertex.

21

Consider the parabola whose equation is y = 3 x^{2} + 3 x - 7. Find the x-intercepts of the parabola in exact form.

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Outcomes

U1.AoS1.2

qualitative interpretation of features of graphs of functions, including those of real data not explicitly represented by a rule, with approximate location of any intercepts, stationary points and points of inflection

U1.AoS1.4

graphs of polynomial functions of low degree, and interpretation of key features of these graphs.

U1.AoS2.7

solution of polynomial equations of low degree, numerically, graphically and algebraically, including numerical approximation of roots of simple polynomial functions using the bisection method algorithm

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