8x-(x-2)(3x+1)-2(x+1)(x-5)的解谁知到怎么做?

8x-(x-2)(3x+1)-2(x+1)(x-5)
=8x-(4x^2-5x-2)-2(x^2-4x-5)
=8x-4x^2+5x+2-2x^2+8x+10
=-6x^2+21x+12=0
2x-7x-4=0
x1=4
x2=-1/2

=8x-(3x+x-6+2)-2(x方+x-5x-5) =8x-3x-x+6-2-2x方-x+5x+5 =-2x方+8x+9

=8x-(3x²-7x-2)-2（x²-4x-5）
=8x-3x²+7x+2-2x²+4x+5
=19x-x²+7

-5x²+21x+12
就是把括号里的先乘出来，再去括号，然后合并同类项，就行了。