May 16, 2012 Adding and Subtracting Rational Expressions DO NOW: Simplify HW: Pg 482 #23-35odds QUIZ Friday!

Go over HW 9.1

When we add or subtract fractions, what do we always need? Common denominators! LCM:

So far we have multiplied and divided rational expressions… Now it’s time to add and subtract! =) First you need to know how to find the least common multiple! Example 1: Find the least common multiple for a 2 b and a 3 b 2 You take the biggest power as the common multiple. LCM: a 3 b 2

Try some more… Find the least common multiple 1.x 4 y 2 and xy 3 2.a 2 b and abc 3.2x 3 and 8xy 2 4.5a 3 b 2 and 10ab You take the biggest power as the common multiple. x4y3x4y3 a 2 bc 8x 3 y 2 10a 3 b 2

Example 2: Finding the common denominator ______ ● ● (x + 2) (x – 1) (x + 2)(x – 1) LCM: (x-1)(x+2) Step 1: Find the least common denominator Step 2: Multiply each term to get the common multiple Step 3: Combine like terms if possible, if not write as one expression.

Practice *Hint: Factor first!

Example 3: Adding and Subtracting Step 1: Find the least common denominator LCM: 8x 3 y 2 Step 2: Multiply each term to get the common multiple What do you need to multiply to both to get 8x 3 y 2 ? ____ ●● 12y 3 5x 2 z Step 3: Combine like terms if possible, if not write as one expression.

Practice