Question 121022
I presume you are able to get to this step: {{{1/a^2 + 1/b^2 + 2/(a*b)}}}
Now, what is the common denominator? {{{a^2*b^2}}}

Multiply each term by what it is missing to form the common denominator:
{{{1/a^2*(b^2/b^2) + 1/b^2*(a^2/a^2) + 2/(a*b)*(a*b/(a*b))}}}.

As you can see, the numerator becomes {{{b^2+a^2+2a*b}}}, and the denominator is {{{a^2*b^2}}}.