先化简,再计算:[(x+1/2)²+(x-1/2y)²](2x²-1/2y²),
运用乘法公式计算:(1)(x-y)(x+y)-(2x-y)²
计算:(1)2/(x+y)+4y/x²-y²(2)x²/x+y-x+y
计算3x[xy-2x(1/y-x/3]+3y(x²-y²)
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
若|x+y-1|+(x-y-2)²=0,求代数式(x+2y)(x-2y)-(2x-y)(-y-2x)的值.
若|x+2y-1|+y²+4y+4=0,求(2x-y)²-2(2x-y)(x+2y)+(x+2y)&
计算(1)3x/8y×16y²/27x² (2)(2xy-x²)÷x-2y/xy 2x-6
计算 1/x²-y²+ 2 /(x-y)²
计算:[(x+¼y)+(x-¼y)](2x²-1/8y²)
计算(x-2y-1)(x-2y+1)-(x-2y-1)²
数学用乘法公式计算(x+y+1)(x+y-1)(2x-y-3)²