I need some help with factoring.?

Question

I'm having a tough time with the questions with two variables in them, so any help with the following would be appreciated:

a) x^2 + 2xy + 2x + y^2 + 2y - 8

b) k^3 - 2(k^2)r - 3kr^2

c) 45x^2 - 80y^2 (i pulled out the GCF, but i'm not sure if you can go any further)

d) 36(a^3)(b^2) + 66(a^2)(b^3) - 210ab^4

e) 4a^2 + 12ab + 9b^2 - 25c^2

Thanks!

Answer 1

a regoup so x² +2xy +y² become (x+y)² then group 2x + 2y so this is 2(x+y) now think of the x+y like one variable a²+2a-8 so that factored would be (a+4)(a-2), then replace a back with x+y  (x+y+4)(x+y-2)

b. k(k²-2kr-3r²) = k(k-3)(k+1)

c.think of middle term as 0xy 5(9x²-16y²) = (3x -4y)(3x+4y)

d pull 6 and ab² from each it will factor

e 4a(a+3b) +(3b-5c)(3b+5c)  this one stumped me