先化简,再求值:3x^3-[x^3+(6x^2-7x)]-2(x^3-3x^2-4x),其中x＝-1/3_数学解答

先化简,再求值:3x^3-[x^3+(6x^2-7x)]-2(x^3-3x^2-4x),其中x＝-1/3

人气：488 ℃　时间：2019-10-19 05:44:47

解答

3x^3-[x^3+(6x^2-7x)]-2(x^3-3x^2-4x)
=3x^3-(x^3+6x^2-7x)-2x^3+6x^2+8x
=3x^3-x^3-6x^2+7x-2x^3+6x^2+8x
=15x
=15×(-1/3)
=-5