设这堆煤为X吨 （1-2/5 x）x（1-5/9）+10=74 3/5x x 4/9 =64 3/5x = 144 x=

（1） x-3/x-2 - x-5/x-4=x-7/x-6 - x-9/x-8 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), x^5+x^4 = (x^3-x)(x^2+x+1)+x^2+x 1x+2x+3x+4x+5x+6x+7x+8x+9x+10x+11x+12x+13x+14x+15x=550 x+2x+3x+4x+5x+6x+7x+8x+9x=9x-8x-7x-6x-5x-4x-3x-2x-x.x等于多少? 1x()+2x()+3x()+4x()+5x()+6x()+7x()+8x()加9x()+10x()=1980 1X?+2X?+3X?+4X?+5X?+6X?+7X?+8X?+9X?+10X?=1980求?是多少 |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（x的平方-6x-9）=x(x-5)X(x-3) 方程(x-1/x-2)-(x-3/x-4)=(x-2/x-3)-(x-4/x-5)解为x=7/2,(1/x-7)-(1/ 方程（x+1)(x+2)(x+3)(x+4)(x+5)(x+6)(x+7)(x^2+8x+9)+64=0