题目

（1）(a-2b+3c)(a+2b-3c)(2)(2x-3y)^2-(y+3x)(3x-y)(3)(2x+y+z)(y-2x-z)(4)2(a-b)^2-a(a-b)

提问时间：2021-05-05

答案

（1）(a-2b+3c)(a+2b-3c)
=[a-(2b-3c)][a+(2b-3c)]
=a²-(2b-3c)²
=a²-4b²+12bc-9c²
(2)(2x-3y)^2-(y+3x)(3x-y)
=4x²-12xy+9y²-9x²+y²
=-5x²-12xy+10y²
(3)(2x+y+z)(y-2x-z)
=[y+(2x+z)][y-(2x+z)]
=y²-(2x+z)²
=y²-4x²-4xz-z²
(4)2(a-b)^2-a(a-b)
=2(a²-2ab+b²)-a²+ab
=2a²-4ab+2b²-a²+ab
=a²-3ab+2b²