Core Connections Algebra 2, 2013
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Core Connections Algebra 2, 2013 View details
2. Section 12.2
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Exercise 97 Page 642

Practice makes perfect
a
Using the function f(x), we want to evaluate for the given value, f( 2). To do this, we need to substitute 2 for x in each instance of the x-variable and simplify the result.

f(x)=x^2+7x
f( 2)= 2^2+7( 2)
f(2)=4+14
f(2)=18

b
Using the function f(x), we want to evaluate for the given value, f( -3). To do this, we need to substitute -3 for x in each instance of the x-variable and simplify the result.

f(x)=x^2+7x
f( -3)=( -3)^2+7( -3)
f(-3)=9-21
f(-3)=-12

c
Using the function f(x), we want to evaluate for the given value, f( -3). To do this, we need to substitute i for x in each instance of the x-variable and simplify the result.

f(x)=x^2+7x
f( i)=( i)^2+7 i
f(i)=-1+7i

d
Using the function f(x), we want to evaluate for the given value, f( -3.5+1.5i). To do this, we need to substitute -3.5+1.5i for x in each instance of the x-variable and simplify the result.

f(x)=x^2+7x
f( -3.5+1.5i)=( -3.5+1.5i)^2+7( -3.5+1.5i)
â–¼
Simplify right-hand side
f( -3.5+1.5i)=( -3.5+1.5i)^2-24.5+10.5i
f(-3.5+1.5i)=(-3.5)^2+2(-3.5)(1.5i)+(1.5i)^2-24.5+10.5i
f(-3.5+1.5i)=(-3.5)^2+2(-3.5)(1.5i)+1.5^2i^2-24.5+10.5i
f(-3.5+1.5i)=12.25-10.5i+2.25i^2-24.5+10.5i
f(-3.5+1.5i)=12.25-10.5i+2.25(-1)-24.5+10.5i
f(-3.5+1.5i)=12.25-10.5i-2.25-24.5+10.5i
f(-3.5+1.5i)=-14.5

e
Using the function f(x), we want to find the value of x given that f(x)=0. To do this, we need to substitute 0 for f(x).

f(x)=x^2+7x
0=x^2+7x
0=x(x+7)
x(x+7)=0
x=0 & (I) x+7=0 & (II)
x=0 x=-7

Therefore, we have two possible values of x such that f(x)=0, x=0 and x=-7.