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11-3 Multiplying Rational
Expressions
Algebra 1
Glencoe McGraw-Hill
Linda Stamper
Because the variables in a rational expression represent
real numbers, the rules for multiplying rational expressions
are the same as the rules for multiplying fractions.
a c
ac
 
b d bd
2x 3x 6x2
 2
3x 4x 12x3
1

2x
Remember you
CAN cross cancel
a multiplication
problem!
1
a c ac
 
b d bd
1
2x 3x
 2 1
3x 4x 2x
2x
Simplify.
The problem.
Factor.
1
3
Cross cancel, if possible.
Multiply numerators
Multiply denominators.
1
3
1

x  2x  1
4
Check if answer is simplified.
Difference
of two
squares.
1
x 3
x 2
x 3
x 2



x2  4 x2  4x  3 x  2x  2 x  3x  1
Notice the
answer is
left in
FACTORED
form!
Simplify.
Example 2
Example 1
5
3
7n 10n

2 14n
5n
y 5
2

2 y2
3y  3y y2  6y  5
Example 3
2x  1
 2x  3
2
2x  x  3
Example 1 Simplify.
1
5
8
7n5 10n3 70n


2 14n
70n3
5n
 n5
If you do not cross
cancel, multiply the
numerators, multiply
the denominators
and then simplify.
Example 2 Simplify.
1
1
2y/2
y 5
 2


2
yy  1 y  5y  1
3y  3y y  6y  5 3/
y 5
2 y2
5
5 1
6
GCF of 3y2  3y
3yy  1

2y
3y  12
Example 3 Simplify.
1
2x  3
2x  1
2x  1

 2x  3 
2



2
x

3
x

1
1
2x  x  3

2x  1
x 1
Remember you
can cancel
factors but not
terms.
White Board
Practice
Simplify.
2
2
56x
4
x
14
1)


7 5x 35x
8x

5
Simplify.
1
1
x 3
x 3 x 3 x 3
2)


 2
x  3 x  9 x  3 x  3x  3
1

x 3
Simplify.
1
2
x 2 6
x 2 6

 
3)
x
x


3
x

2
3x  6
2

x
Simplify.
1
1
x4
3x  1
x4

 3x  3 
4) 2
1
x  4 x  1
x  5x  4
3
Simplify.
5)
-1
2
-1
y  3y  28 10x  5 y  7 y  4  52x  1


2
4  y 4  y   1  2x 
16  y
1  2x
5y  7 

4  y 

5y  7 
y4
Simplify.
1
6)
x 7 x 3
x 7 x 3



x x7
x 7x
x 3

x
Simplify.
1
7)
1
x  5 4x  6
x  5 4x  6





2x  12 8x  40 2 x  6 8x  5
1

4
2
Simplify.
1
2
1
x  5x  2
1
1
8) x  7 x  10 


2



x

7
x

5
8x  2
x  2x  35 8x  16

1
8x  7 
Simplify.
9)
2
2
1
1
1
x  5x  4 2x  6x

x  4 x  1 2xx  3
 2


2


x
x

3
x  4 x  1
x  3x x  3x  4
2x  1

x 1
Simplify.
1
1
1
2
2
x

6
x

8
2
x
 x  1 x  4 x  2 x  22x  1
10)


 2
2
2x  9x  4 x  3x  2 2x  1x  4  x  2x  1
x 2

x 1
11-A3 Page 592-594 # 9–22,49-53.