[SOLVED] Algebra homework - please check if these are right ->

I'm working on my second homework, as I've mentionned before this is a math class I'm taking to get myself up to college math. I'm starting my master's in Human Ress, but I haven't done math since high school, about 20 years ago. My brain just doesn't work as good as it used too? (Thinking)

If someone would just check if those 3 answers are correct, that would be of great help.

If:

P1= 12x^2-6xy+9y^2

P2= -2x^2+3xy-4y^2

P3= 2x-y^2

And:

M1= -3xy

1) P3-P2

=(2x-y^2)-(-2x^2+3xy-4y^2)

=(2x-y^2)+(2x^2-3xy+4y^2)

=2x+(-y^2+4y^2)+2x^2-3xy

=2x+3y^2+2x^2-3xy

2) P2XP3

=(-2x^2+3xy-4y^2) (2x-y^2)

=(-2x^2)x2x+(-2x^2)x(-y^2)+3xyx2x+3xyx(-y^2)+(-4y^2)x2x+(-4y^2)x(-y^2)

=(-4x^3)+2x^2y^2+6x^2y-3xy^3-8xy^2+4y^4

3)P1/M1

=12x^2-6xy+9y^2

----------------

-3xy

=12x^2 -6xy 9y^2

------ + ----- + ------

-3xy -3xy -3xy

=-4xy^-2+0.5+-3x^-1y

=-4xy^-2-x^-1y+0.5

=-7x^-1y^-1+0.5

=0.5

----

7xy

Those are the first three, I'm trying my best not to check everything with you guys because the homework is extensive and I've already had to ask for a prolongation, which cost me 60$ more (on top of the 350$+ they charged for the class), so believe me when I say that this is important for me and you guys are not wasting your time helping me out.

Thank you so much

Neenoon