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1.5A Polynomial functions and complex zeros

Worksheet
What do you remember?
1

What is a zero of a polynomial function?

2

Define the term 'multiplicity' in the context of polynomial function zeros.

3

What determines the number of complex zeros a polynomial function has?

4

What does it mean for a polynomial function's graph to have an x-intercept at a point (a,\, 0)?

5

How does the presence of a non-real zero affect the other zeros of a polynomial function?

Let's practice
6

Determine the real and complex zeros of the following polynomial functions:

a
f(x) = x^3 - 6x^2 + 11x - 6
b
g(x) = x^4 - 2x^2 + 1
c
h(x) = x^3 - 3x^2 - 4x + 12
d
k(x) = x^4 - 5x^2 + 4
7

For the given polynomial functions, identify the zeros and their multiplicities.

a
f(x) = x^3 - 9x^2 + 27x - 27
b
f(x) = 4x^4 - 4x^2
c
f(x) = (3x - 6)^2(x + 4)
d
f(x) = x^5 - 5x^4 + 10x^3 - 10x^2 + 5x
8

Determine the zeros and their multiplicities for the following polynomial functions:

a
f(x) = (x^2 - 4)(x + 2)^3
b
f(x) = -2(x - 1)^4(x + 5)^2
c
f(x) = 3(x + 3)(x - 2)^3
9

Consider the following polynomial function: f(x) = x^3 - 9x^2 + 26x - 24

a

Identify the x-intercepts of the function and their corresponding points (a,\, 0) on the graph.

b

Write the polynomial function in factored form based on the x-intercepts found in part a.

10

For each of the following polynomial functions:

i

Determine the multiplicity of each zero.

ii

Describe the behavior of the graph near each zero.

a
f \left( x \right) = (x + 5)^3(x - 1)^2
b
f \left( x \right) = x^4 (x - 3)(x + 4)^2
c
f \left( x \right) = (2x^2 + 5x - 3)^4
d
f \left( x \right) = (x^2 - 1)^3(x^2 - 4)
11

The graph of a polynomial function is shown.

a

Identify the multiplicity of each zero.

b

Describe the behavior of the graph near each zero.

-4
-3
-2
-1
1
2
3
4
x
-160
-140
-120
-100
-80
-60
-40
-20
20
40
y
12

A polynomial function is represented by the following table of values. Calculate the successive differences and determine the degree of the polynomial function:

x-5-3-1135
y951159
Let's extend our thinking
13

The polynomial function k(x) = x^3 - 3x^2 - 4x + 12 has a complex zero 2 + i. Write the polynomial in factored form using its real and non-real zeros.

14

Consider the polynomial function m(x) = x^5 - 7x^3 + 6x. What is the significance of the polynomial having a zero with even multiplicity? How does this affect the graph of the function?

15

A polynomial function has a degree of 3 and has zeros at x = -1, x = 2, and x = 4. The zero at x = -1 has a multiplicity of 2.

a

Write the polynomial function in standard form.

b

Determine the regions of the domain where the function is positive, negative, and zero.

16

Consider a polynomial function q(x) with the following properties:

  • Has a leading coefficient of 1

  • Has zeros at x = -2, x = 1 + i, and x = 1 - i

a

Write the polynomial function q(x) in factored form.

b

Determine the real and complex zeros of the function and their multiplicities.

c

Identify any connections between the complex zeros and their conjugates, using the complex conjugate zeros theorem.

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Outcomes

1.5.A

Identify key characteristics of a polynomial function related to its zeros when suitable factorizations are available or with technology.

1.5.B

Determine if a polynomial function is even or odd.

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