(2x-1)(x+2)-(x-2)²,化简.x=-一又三分之一_数学解答

(2x-1)(x+2)-(x-2)²,化简.
x=-一又三分之一

人气：493 ℃　时间：2020-01-28 14:37:50

解答

解
(2x-1)(x+2)-(x-2)²
=(2x²+3x-2)-(x²-4x+4)
=(2x²-x²)+(3x+4x)+(-2-4)
=x²+7x-6
=(-4/3)²+7×(-4/3)-6
=(16/9-28/3-6
=-68/9-54/9
=-122/9