ok, so remember
[tex]x^{-m}= \frac{1}{x^m} [/tex]
and [tex](x^m)(x^n)=x^{m+n}[/tex]
so
[tex](a^{-2})+(a^{-1})(b)- (\frac{b^2}{a^2}) (b^{-1})[/tex]=
[tex]( \frac{1}{a^2} )+( \frac{b}{a} )-( \frac{(b^2)(b^{-1})}{a^2} )[/tex]=
[tex]( \frac{1}{a^2} )+( \frac{b}{a} )-( \frac{b^1}{a^2} )[/tex]
common denomenator
times 2nd fraction by a/a
[tex]( \frac{1}{a^2} )+( \frac{ab}{a^2} )-( \frac{b^1}{a^2} )[/tex]
add/subtract
[tex] \frac{1+ab+b}{a^2} [/tex]
