简再求值:(x+2)(x²+5x-10)-(x+2)²(x-1),其中x =1又2分之1
(x+2)(x²+5x-10)-(x+2)²(x-1)
= (x+2)(x²+5x-10)-(x+2)(x²+x -2 )
= (x+2) ( x²+5x-10-x² -x+2)
= (x+2 ) (4x -8)
= 4 (x+2) (x-2)
代入 x = 3/2
原式
= 4 x 7/2 x ( - 1/2)
= - 7
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