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January 29, 2015

January 29, 2015

Posted by **Alaska Diamond** on Thursday, August 1, 2013 at 7:22pm.

5/8+√7

- algebra -
**Steve**, Thursday, August 1, 2013 at 8:29pmThe main point is to recall that (a-b)(a+b) = a^2-b^2

So, if you want to get rid of roots in the denominator, multiply top and bottom by the "conjugate" expression

(8+√7)(8-√7) = 8^2 - √7^2 = 64-7 = 57

So,

5/(8+√7) = 5(8-√7)/((8+√7)(8-√7))

= 5(8-√7)/57

= (40 - 5√7)/57

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