1. Multiplying, Dividing, Adding, Subtracting Rational Expressions
MA 1128: Lecture 14 – 11/3/14
Multiplying, Dividing, Adding, Subtracting
Rational Expressions

2. Multiplying and Dividing Fractions
Rational expressions differ from regular fractions in that they have variables.
These variables represent numbers, however,
so the basic rules that apply to fractions also apply to rational expressions.
For fractions, multiplying is easy.
Here, think of the 2 and 3 as being multiplied (top),
and the 4 and 5 are divided (bottom).
When you divide, you should do the opposite.
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3. Dividing: Invert and Multiply
Remember: To divide fractions, invert and multiply.
With rational expressions, it goes the same way. Look at these three examples.
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4. Practice Problems Multiply or Divide. Simplify. Answers on next slide.

5. Answers to Practice Problems on last slide
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6. Adding and Subtracting
With regular fractions, we need a common denominator before we add or subtract.
Consider these three examples.
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7. Adding and Subtracting (cont.)
For rational expressions, we do the same.
If we have a common denominator, just add or subtract the numerator.
Remember to subtract every term!
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8. Practice Problems Click for answers:
1) 1; 2) x – 1; 3) [x-3]/[x+1]; 4) 1.
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