Perform the indicated operations and simplify. (Note: The answers should have no negative exponents)
1) (3mn^2 + 2mn - 3m^2n^2) - (3m^2n - 6mn^2) - (m^2n - 6m^2n^2)
2) 2x (A+B)y - (A+B)y^2 / 8(A+B)
First thing you want to do is distrubute those negatives signs...doing that, you'll get
$\displaystyle mn^2 + 2mn - 3m^2n^2 - 3m^2n + 6mn^2 - m^2n + 6m^2n^2$
Now, you should group like terms...m squared, n squareds go together, m squared ns should go together...so on
$\displaystyle 6m^2n^2 - 3m^2n^2 - 3m^2n - m^2n + 6mn^2 + 3mn^2 + 2mn$
Now, combine like terms
$\displaystyle [6m^2n^2 - 3m^2n^2] [- 3m^2n - m^2n] [+ 6mn^2 + 3mn^2] + 2mn$
gets
$\displaystyle 3m^2n^2 - 4m^2n + 9mn^2 + 2mn$
Now, about this. Is this supposed to be
2) 2x (A+B)y - (A+B)y^2 / 8(A+B)
$\displaystyle 2x(A+B)y - (A+B)\frac{y^2}{8}(A+B)$ or
$\displaystyle 2x(A+B)y - \frac{(A+B)y^2}{8(A+B)}$
?? Can't tell by the way you wrote it...