If anybody could help, I have a math exam tomorrow, and I'm working on the review...but I've been having alot of trouble. Usually I can figure this stuff out by studying my notes...but I'm at a loss. Any help would be appreciated. The first three are problems that I don't understand, the rest are ones that I've completed, but I'm not sure if they're right.

1. $\displaystyle x^2+x=20 $

2. Solve by quadratic formula:

$\displaystyle 2x^2-5x=2 $

3. Solve by completing the square:

$\displaystyle x^2+8x-9=0 $

And the ones that I've completed, but not sure if they're right...I would appreciate if you could check these out.

1. $\displaystyle 6y \sqrt{27x^3y} - 3x \sqrt{12xy^3} + xy \sqrt{4xy} $

I got:

$\displaystyle 12xy \sqrt{3xy} + 2xy \sqrt{xy} $

2. $\displaystyle (4 \sqrt{x} + 3 \sqrt{y})(2 \sqrt{x} - 5 \sqrt{y}) $

I got:

$\displaystyle 8x-14 \sqrt{xy} - 15y $

3. $\displaystyle \frac{\sqrt 75a^8b^5}{\sqrt 5ab^2} $

I got:

$\displaystyle b \sqrt{15a^7b} $