因式分解5道题.-ab²+4abc-3ac²（x-y）²3（x-y）-40x²-4y²+x+2yx²-6x+9-y²3a²+bc-3ac-ab第二题是（x-y）²-3（x-y）-40

因式分解5道题.
-ab²+4abc-3ac²
（x-y）²3（x-y）-40
x²-4y²+x+2y
x²-6x+9-y²
3a²+bc-3ac-ab
第二题是（x-y）²-3（x-y）-40

-ab²+4abc-3ac²
=-a(b²-4bc+3c²)
=-a(b-3c)(b-c)
（x-y）²-3（x-y）-40
=[(x-y)-8][(x-y)+5]
=(x-y-8)(x-y+5)
x²-4y²+x+2y
=(x+2y)(x-2y)+(x+2y)
=(x+2y)(x-2y+1)
x²-6x+9-y²
=(x-3)²-y²
=(x-3+y)(x-3-y)
3a²+bc-3ac-ab
=3a²-3ac+bc-ab
=3a(a-c)-b(a-c)
=(a-c)(3a-b)