Alice
Multiply the numerator and the denominator of the fraction by (a+1) then follow the algebraic rules of multiplication and you will get the result you want.
Alice our purpose is to eliminate the surds from the denominator...
if you have a^2 alone and then 1/a a fraction alone then no problem multiply the fraction only by (root5 +1) (num +denom) and then expand a^2 and add them all together