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)
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