EXAMPLE 4 Simplifying a Variable Expression

=14x7xy

2 7 x7 x y

Factor numerator and denominator.

Divide out common factor.

Simplify.= 2y

2 7 x7 x y

=

1

1

1

1

EXAMPLE 5 Evaluating a Variable Expression

Evaluate powers and simplify.

Factor numerator and denominator.

Simplify.

Evaluate the expression when x = 5.–4x3

2x

Divide out common factor.

Substitute 5 for x.

= –2x2

= –2(5)2

= –50

–1 2 2 x x x2 x

=1

1

1

1

–4x3

2x =–1 2 2 x x x

2 x

GUIDED PRACTICE for Examples 4 and 5

Simplify the variable expression. Then evaluate for x = – 2 and y = 3.

12.

4xy6x

= 2

=2y3

GUIDED PRACTICE for Examples 4 and 5

Simplify the variable expression. Then evaluate for x = – 2 and y = 3.

13.

32y8xy = 4

y

= 43

GUIDED PRACTICE for Examples 4 and 5

Simplify the variable expression. Then evaluate for x = – 2 and y = 3.

14.

3x3y 6x = x2y

3

= 4

GUIDED PRACTICE for Examples 4 and 5

Simplify the variable expression. Then evaluate for x = – 2 and y = 3.

15.

5x2y10xy = x

2

= –1