15a^3b^2+5a^2b
=5a²b×3a+5a²b×1
=5a²b(3a+1)
-20a^2b^2x-45bxy
= -5bx×4a²b+-5bx×9y
=-5bx(4a²b+9y)
2m(a-b)-3n(b-a)
=2m(a-b)+3n(a-b)
=(a-b)(2m+3n)
(a-3)^2+(3-a)
=(a-3)²-(a-3)
=(a-3)(a-3-1)
=(a-3)(a-4)
a(x-y)+b(y-x)+c(x-y)
=a(x-y)-b(x-y)+c(x-y)
=(x-y)(a-b+c)
a^n+2+a^n+1-a^n
=a^n(a²+a-1)
1/2a^2b^3-2a^2b+3ab^2
=1/2ab(ab²-4a+6b)
-5a^2b^3+20ab^2-5ab
=-5ab(ab²-4b+1)
5m(m-n)^4-10mn(n-m)^3
=5m(m-n)^4+10mn(m-n)³
=5m(m-n)³(m-n+2n)
=5m(m-n)³(m+n)
(a+b)y+(b+m)y+(a+m)y
=y(a+b+b+m+a+m)
=2y(a+b+m)