Core Connections Algebra 2, 2013
CC
Core Connections Algebra 2, 2013 View details
Chapter Closure

Exercise 119 Page 48

a

To find f(5), we have to substitute x=5 into f(x)=sqrt(x+4) and evaluate.

f(x)=sqrt(x+4)
f( 5)=sqrt(5+4)
f(5)=sqrt(9)
f(5)=3

b

To find g(-1), we will substitute x=-1 in g(x)=x^2-x and evaluate.

g(x)=x^2-x
g( -1)=( -1)^2-( -1)
g(-1)=1-(-1)
g(-1)=1+1
g(-1)=2

c

This time we are given the value and asked to find x when the equation equals 10. To find it, we will substitute f(x)=10 into the given rule and solve for x.

f(x)=sqrt(x+4)
10=sqrt(x+4)
LHS^2=RHS^2
10^2=(sqrt(x+4))^2
10^2=x+4
100=x+4
96=x
x=96

When x=96, the value of the function f(x) equals 10.

d

This time we are given the value and asked to find x when the equation equals 6. To find it, we will substitute g(x)=6 into the given rule and solve for x.

g(x)=x^2-x
6=x^2-x
0=x^2-x-6
x^2-x-6=0

We got a quadratic equation in terms of only the x-terms. To solve the equation, first we should identify the values of a, b, and c.

x^2-x-6=0 ⇔ 1x^2+( -1)x+( -6)=0 We see that a= 1, b= -1, and c= -6. Let's substitute these values into the Quadratic Formula.

x=- b±sqrt(b^2-4ac)/2a
x=-( -1)±sqrt(( -1)^2-4( 1)( -6))/2( 1)
Solve for x and Simplify
x=1±sqrt((-1)^2-4(1)(-6))/2(1)
x=1±sqrt(1-4(1)(-6))/2(1)
x=1±sqrt(1-4(-6))/2
x=1±sqrt(1+24)/2
x=1±sqrt(25)/2
x=1±5/2

The solutions for this equation are x= 1± 52. Let's separate them into the positive and negative cases.

x=1± 5/2
x_1=1+5/2 x_2=1-5/2
x_1=6/2 x_2=-4/2
x_1=3 x_2=-2

Using the Quadratic Formula, we found that the solutions of the given equation are x_1=3 and x_2=-2.