计算:(x-y)(1/9x-y)-(1/3x-y)(1/3x+y)
计算:1/(2x) - 1/(x+y)((x+y)/(2x) - x - y)
先化简再求值:(x-2y)²-(x+2y)(x-2y)-(x-3y)(x-y).其中x²+9y
计算:(2/3x根号下9x+6x根号下y/x)+(y根号下x/y-x的平方根号下1/x)=
计算:(x-y)(1/9x-y)-(1/3x-y)(1/3x+y)
计算(1)x/x+y-x/x-y (2)a+2+4/a+2 (3)x^2-y^2/xy÷(x+y)
已知:3x=8y.求(1)x+y/y (2)2x+3y/x-2y
化简:(x+y)+(2x+y/1*2)+(3x+y/2*3)+...+(9x+y/8*9)
1) (x+y)^2-(x+y)^3 2) (x-y)^2-(x-y)^3 3)(x-y)^2-(y-x)^3 因式分解
利用因式分解计算1/2x(x-y)^2-1/5y(x-y)
运用乘法公式计算:(1)(x-y)(x+y)-(2x-y)²
计算1):(-x-y) (x+y)二次方 2)(y-x)(x-y)的三次方
计算:(3x-4y)-[-(2y+x)+(x-3y)]-6x