Core Connections Algebra 2, 2013
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Core Connections Algebra 2, 2013 View details
2. Section 8.2
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Exercise 87 Page 396

Practice makes perfect
a

The function has two roots, which means we can write the expression as a second degree function in factored form.

y=a(x-b)(x-c) In this equation, b and c are the equation's roots and a is the stretch factor, which we will assume is 1. From the exercise, we know that the roots are a=-3+i and b=3-i. Let's substitute the equation's roots in our equation and simplify the right-hand side.

y=(x-b)(x-c)
y=(x-( - 3+i))(x-( - 3-i))
â–¼
Simplify right-hand side
y=(x+3-i)(x+3+i)
y=x^2+3x+ix+3x+9+3i-ix-3i-i^2
y=x^2+6x+9-i^2
y=x^2+6x+9-(-1)
y=x^2+6x+9+1
y=x^2+6x+10

b

Like in Part A, we have two roots, which means the function we are looking for is a second degree function. This means we can write it in factored form.

y=a(x-b)(x-c) Let's substitute our roots into this equation and simplify. We will assume a stretch factor of a=1.

y=(x-b)(x-c)
y=(x-( 5+sqrt(3)))(x-( 5-sqrt(3)))
â–¼
Simplify right-hand side
y=(x-5-sqrt(3))(x-5+sqrt(3))
y=x^2-5x+sqrt(3)x-5x+25-5sqrt(3)-sqrt(3)x+5sqrt(3)-3
y=x^2-10x+22

c

In this case we have three solutions, which means we can write the function in the following way.

y=a(x-b)(x-c)(x-d) In this form, b, c, and d are our roots. By substituting these into the equation, we can determine the function. Again, we will assume a stretch factor of a=1.

y=(x-b)(x-c)(x-d)
y=(x-(- 2))(x-sqrt(7))(x-(- sqrt(7)))
â–¼
Simplify right-hand side
y=(x+2)(x-sqrt(7))(x+sqrt(7))
y=(x+2)(x^2-(sqrt(7))^2)
y=(x+2)(x^2-7)
y=x^3-7x+2x^2-14
y=x^3+2x^2-7x-14

d

Like in Part C, we have three roots, which means we can write the equation in factored form in the following way.

y=a(x-b)(x-c)(x-d) In this form, b, c, and d are our roots. By substituting these into the equation, we can determine the function. We will assume a stretch factor of 1.

y=(x-b)(x-c)(x-d)
y=(x-4)(x-(- 3+i))(x-(- 3-i))
â–¼
Simplify right-hand side
y=(x-4)(x+3-i)(x+3+i)
y=(x-4)(x^2+3x+ix+3x+9+3i-ix-3i-i^2)
y=(x-4)(x^2+6x+9-i^2)
y=(x-4)(x^2+6x+9-(-1))
y=(x-4)(x^2+6x+9+1)
y=(x-4)(x^2+6x+10)
y=x^3+6x^2+10x-4x^2-24x-40
y=x^3+2x^2-14x-40