4(x^2-5x)-5(2x^2+3x)化简,我怎么算都=-6x^2-5x

x+2x+3x+4x+5x+6x+7x+8x+9x=9x-8x-7x-6x-5x-4x-3x-2x-x.x等于多少? x^5+x^4 = (x^3-x)(x^2+x+1)+x^2+x 2x+3x+4x+5x+x+6x+7x=100 |X-1|+|X-2|+|X-3|+|X-4|+|X-5|+|X-6|+|X-7|+|X-8|+|X-9|+|X-10| 7x(x-6)+3x=4x(2x+5)怎么解这个方程 x+2/x+1-x+3/x+2-x+4/x+3+x+5/x+4 解方程x/(x-2)=2x/(x-3)+(1-x)/(x-5x+6) 已知1+x+x^2+x^3=0,求x+x^2+x^3+x^4+x^5+x^6+x^7+x^8的值 y=(x-1)(x-2)(x-3)(x-4)(x-5)(x-6)(x-7)(x-8)(x-9)(x-10)的导数在x=1 设函数f(x)=(x-1)(x-2)(x-3)(x-4)(x-5)(x-6)(x-7)(x-8)(x-9)(x-10), 解方程(x-2)/(x-3)-(x-3)/(x-4)=(x-5)/(x-6)-(x-6)/(x-7) 解方程:(x+3)/(x+2)-(x+5)/(x+4)=(x+7)/(x+6)-(x+9)/(x+8)