Rationalizing the Denominator
Example 1
Simplify:
Solution |
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Factor the radicand. |
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The radical in the denominator is a cube root. To rationalize the
denominator, we want to make the radicand a perfect cube.
- 2 occurs twice as a factor. To make a perfect cube, we multiply by 2.
- w occurs once as a factor. To make a perfect cube, we multiply by w2.
We multiply by 1 written in the form
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Multiply the numerators and multiply
the denominators.
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Simplify the denominator. |
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So, |
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Suppose we have a radical expression such as
Recall that when we multiply conjugates, the result is always a rational
number.
Therefore, to eliminate the radical in the denominator of the expression,
we multiply the numerator and denominator by
, the conjugate
of the denominator.
Example 2
Simplify:
Solution |
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To rationalize the denominator
we multiply the numerator
and denominator by
, the conjugate of x
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Multiply the numerators and
multiply the denominators.
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Remove the parentheses. |
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Simplify the denominator.
The two middle terms add
to zero. |
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So, |
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