Posted by **-Untamed-** on Monday, October 3, 2011 at 9:40pm.

About rationalizing denominator, is it true that you can't always multiply by the same square root denominator to get a perfect square?

- Calculus -
**Steve**, Tuesday, October 4, 2011 at 8:56am
yes, because (√n)² = n

so, multiplying the root by itself gets rid of the root.

If the denominator is not just a root, but something like √m + n, then you need to multiply by √m - n, since

(√m + n)(√m - n) = m - n²

also, you sometimes have to use

(√m + √n)(√m - √n) = m - n

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