help me with this

Question

\frac{2}\sqrt{5}+\sqrt{7}                   Rationalize the denominator   

Answer 1

Multiply numerator and denominator by √5 - √7.  This will give a difference of squares in the denominator.

 

2 / (√5 + √7) = 2(√5 - √7) / [(√5 - √7)(√5 + √7)] = 2(√5 - √7) / (5 - 7)

 

= 2(√5 - √7) / (-2) = √7 - √5