hardaway7 wrote:

I understand the 6(sqrt7) but not sure why we should multiply 2/(8+3sqrt7) by (8-3sqrt7)... why the MINUS...

THANKS ALL FOR YOUR HELP!!

Whenever you see a root in the denominator, the first instinct should be to get rid of it. Its easy to get rid of (a + Vb) or (a -Vb) in the denominator, since you can simply use the a^2-b^2 formula, and hence bring your root to the numerator, where its easier to manage.

1/(a+Vb)

= (a-Vb)/{(a+Vb)(a-Vb)} .... multiplying both numerator and denominator by (a-Vb)

= (a -Vb) / a^2 - b