去括号合并:(1)3x^3-[x^3+(6x^2-7x)]-2(x^3-3x^2-4x)(2)(3x^2-4y^2)+[-(x^2_数学解答

去括号合并:(1)3x^3-[x^3+(6x^2-7x)]-2(x^3-3x^2-4x)
(2)(3x^2-4y^2)+[-(x^2-2xy-y^2)]-[-(3x-2xy-y^2)]

人气：405 ℃　时间：2019-12-10 05:35:26

解答

(1)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^3-2x^3-6x^2+6x^2+7x+8x=15x(2)(3x^2-4y^2)+[-(x^2-2xy-y^2)]-[-(3x-2xy-y^2)]=3x^2-4y^2-x^2+2xy+y^2+3x-2xy-y^2=3x^2-x^2-4y^2+y^2...