x-y=1,x²+y²=5,

已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y 已知x²+y²+5=2x+4y,求代数式（2x²-（x+y)(x-y))x((x+y-1) 已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)² (1)已知x+y=6,x²-y²=5,求x-y的值（2）若x+y=3,x²+y² [(y-2x)(-2x-y)-4(x-2y)²]*2y,其中x=1,y=2 先化简,再求值[(x+2y)²-2(x+y)(x-y)-5y²]÷(2x),其中x=-2,y=1\2 若|x+2y-1|+y²+4y+4=0,求（2x-y）²-2（2x-y)(x+2y)+(x+2y)& x²+xy/(x-4y)(x+y),其中x=4,y=-1 [2x²-(x+y) (x-y)] [(-x-y) (y-x)+2y²] 其中x=1,y=2 化简求值 【2x²-(x+y)(x-y)][(x+y-1)(x-y+1)+1-2y],其中x=-1,y=-2 若|x+y-1|+（x-y-2)²=0,求代数式（x+2y)(x-2y）-（2x-y)(-y-2x)的值. 先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y