Consider the fraction
. Multiply this fraction by 1. This is written
. But 1
can be rewritten as
.
The answer,
, is the reduced form. Notice that in
there is no factor common to both the numerator and denominator. This reasoning provides justification for the following rule.
Cancelling
Multiplying or dividing the numerator and denominator by the same nonzero number does not change the value of a fraction.
The process
We can now state a process for reducing a rational expression.
Reducing a rational expression
- Factor the numerator and denominator completely.
- Divide the numerator and denominator by all factors they have in common, that is, remove all factors of 1.
Reduced to lowest terms
- A rational expression is said to be
reduced to lowest terms when the numerator and denominator have
no factors in common.
Sample set a
Reduce the following rational expressions.
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The expression
is the reduced form since there are no
factors common to both the numerator and denominator. Although there is an
in both, it is a
common term , not a
common factor , and therefore cannot be divided out.
CAUTION — This is a common error:
is
incorrect!
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Since
is a common factor to both the numerator and denominator, we divide both by
. Since
, we get 1 in the numerator.
Sometimes we may reduce a rational expression by using the division rule of exponents.
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Practice set a
Reduce each of the following fractions to lowest terms.
Excercises
For the following problems, reduce each rational expression to lowest terms.
For the following problems, reduce each rational expression if possible. If not possible, state the answer in lowest terms.
Excercises for review