1) xk-xy-x²+yk = (xk+yk) - (xy+x²) = k (x+y) -x (y+x) = (x+y)(k-x)
2) 3x-3m-xy+my = (3x-3m) - (xy-my) = 3·(x-m) - y·(x-m) = (x-m)·(3-y)
3) 2xy+3ac+6xc+ay = (ay+2xy) + (3ac+6xc) = y· (a+2x) +3c· (a+2x) =
= (a+2x)(y+3c)
4) 2y²-3y+4ay-6a = ( 2y²-3y) + (4ay-6a) = y( 2y-3) + 2a(2y-3) = (2y-3)(y+2a)
5) ay+ax-5y-5x = (ay+ax)-(5y+5x) = a(y+x) - 5·(y+x) = (y+x)(a - 5)
