8X^2-(X-2)(3X+1)-2(X+1)(X-5)其中X=-2先化解再求值_数学解答

8X^2-(X-2)(3X+1)-2(X+1)(X-5)其中X=-2
先化解再求值

人气：368 ℃　时间：2020-06-25 03:50:22

解答

原式=8X^2-(3X^2-5X-2)-2(X^2-4X-5)
=8X^2-3X^2+5X+2-2X^2+8X+10
=3X^2+13X+12
=3×(-2)^2+13×(-2)+12
=12-26+12
=-2