Warm-up:Here is an example to help you do this warm-

up.

Homework:

9.c add and subtract rational expressions

After this lesson you will be able to…Find the least common denominator for two

or more rational expressionsBuild up the fractions so that they all have

the LCDAdd or subtract the fractionsTo add or subtract fractions to simplify

complex fractions

BIG IDEA!!!You can only add/subtract fractions

with the same denominator!

Procedure:If the fractions have the same

denominator…1. Add/Subtract the numerators.

WATCH OUT! Minus signs distribute!

1. Keep the same denominator.2. Reduce answer if possible.

Example 1:3 4 2

30 30m n m n

n n

Example 2:

2 2

2 5 310 10

y x yx y x y

If the fractions don’t have the same denominators…You MUST make them have the same

denominator before you can add or subtract them.

Building a Least Common Denominator (LCD)BIG IDEA!!!

An LCD will show the factors of both denominators!

PROCEDURE:1. Factor each denominator completely.2. Multiply the top and bottom of each

fraction by whatever factors are missing from that denom.

3. Rewrite as one large fraction. This will help you avoid sign errors.

4. Multiply out the numerator and then combine like terms.

5. Factor and reduce if possible.

Example 3:

Example 4:

Example 5:

Example 6:

Example 7:

2 2

5 24 5 14

x xx x x

Simplifying Complex FractionsExample 8:

Example 9:

Homework:HW ST 9.c both sides