# Essay on Biia4e Ppt 07 03

Submitted By 3256
Words: 1206
Pages: 5

Section 7.3
Subtracting
Rational
Expressions
with the Same
Denominator

1

2

Now, we will practice adding and subtracting rational expressions. Remember that when adding or subtracting fractions, it is necessary to rewrite the fractions as fractions having the same denominator, which is called the common denominator for the fractions being combined. In this section, we will be combining fractions under addition or subtraction that already share the same denominator.

3

Common Denominators
If P and Q are rational expressions, then
R
R
P Q P Q
 
R R
R
To add rational expressions with the same denominator, add numerators and place the sum over the common denominator. If possible, simplify the result.

4

Add: 3x  1  5 x  6

EXAMPLE

7

3x 1 5 x  6

7
7
3x  1  5 x  6

7
8x  5

7

7

Add numerators. Place the sum over the common denominator.

Combine like terms. Factor and simplify if possible. This does not simplify.

5

Add: 3x  1  5 x  6

EXAMPLE

7

3x 1 5 x  6

7
7
3x  1  5 x  6

7
8x  5

7

7

Add numerators. Place the sum over the common denominator.

Combine like terms. Factor and simplify if possible. This does not simplify.

6

EXAMPLE

x 2 1 5x  7

x 1 x 1 x 2 1  5x  7

x 1 x 2  5x  6

x 1
( x  1)( x  6)

x 1
x  6

x 2 1 5x  7

x 1 x 1

Add numerators. Place the sum over the common denominator.

Combine like terms.

Factor and simplify.

7

EXAMPLE

x 2 1 5x  7

x 1 x 1 x 2 1  5x  7

x 1 x 2  5x  6

x 1
( x  1)( x  6)

x 1
x  6

x 2 1 5x  7

x 1 x 1

Add numerators. Place the sum over the common denominator.

Combine like terms.

Factor and simplify.

8

EXAMPLE

x2  2x x2  x
 2
.
Add: 2 x  3x x  3x
SOLUTION

x2  2x x2  x
 2
2
x  3x x  3x x2  2x  x2  x

x 2  3x
2x2  x
 2 x  3x x 2 x  1

x  x  3

This is the original expression.
Add numerators. Place this sum over the common denominator. Combine like terms.
Factor.

9

CONTINUED

x 2 x  1

x  x  3
2x  1

x 3

Factor and simplify by dividing out the common factor, x.
Simplify.

10

Objective #1: Example

11

Objective #1: Example

12

Objective #1: Example

13

Objective #1: Example

14

15

Subtracting Rational Expressions
Subtracting Rational Expressions with
Common Denominators
If P and Q are rational expressions, then
R

R

P Q P Q
 
.
R R
R

To subtract rational expressions with the same denominator, subtract numerators and place the difference over the common denominator. If possible, factor and simplify the result.

16

Subtracting Rational Expressions
EXAMPLE
2

x  1 5 x  13

x2 x2 x 2  1  (5 x  13)

x2 x 2  1  5 x  13

x2 x 2  5 x  14

x2
( x  7)( x  2)

x2
x  7

Subtract:

x 2  1 5 x  13

x2 x2 Subtract numerators. Place the difference over the common denominator. Remove