SECTION 7.2
Adding and Subtracting
Rational Expressions
RATIONAL  FRACTIONAL!
So, we will need Common Denominators
before we can Add or Subtract!!!
 Remember to SIMPLIFY the answers!!!
 Add or Subtract:
 1.
4x – 3y - 2x – 5y
3x – 2y
3x – 2y


2.
r2 – 3r
+ 5r – 15
r2 – 6r + 9
r2 – 6r + 9
TO FIND THE LCD:
Factor all denominators completely. (Prime
factorization)
 Write a product that contains each unique
factor the greatest number of times that
that factor occurs.

Then, multiply each rational expression by
whatever is needed to achieve the common
denominator.
 Add or Subtract, and simplify the answer.

ADD OR SUBTRACT
1.
11 + 13
12a6b3 18a4b5

3.
4n
+ 5
n2 + 14n + 49 n + 7

4.
v2 + 4v
+
3
v2 + 8v + 16
3v + 12

5.
x – 5y - 4x – 6y
x–y
y–x

2.

y
- y
y–3 y–4