1.解方程.(x-1)(x-2)+(x-2)(x+2)=2(x-3)(x+3)-22.计算:4x(x的平方-2x-1)+x(2x+_数学解答

1.解方程.(x-1)(x-2)+(x-2)(x+2)=2(x-3)(x+3)-2
2.计算:4x(x的平方-2x-1)+x(2x+5)(5-2x)

人气：298 ℃　时间：2020-03-07 15:53:10

解答

(x-1)(x-2)+(x-2)(x+2)=2(x-3)(x+3)-2
(x-2)(x-1+x+2)=2(x^2-9)-2
(x-2)(2x+1)=2x^2-18-2
2x^2-4x+x-2=2x^2-20
-3x=-18
x=6
4x(x^2-2x-1)+x(2x+5)(5-2x)
=4x^3-8x^2-4x-x(2x+5)(2x-5)
=4x^3-8x^2-4x-x(4x^2-25)
=4x^3-8x^2-4x-4x^3+25x
=8x^2+21x