若x-y=-4,求x^2+y^2/2 -xy （注意是二分之x^2+y^2） 用乘法公式解

若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 如果|X|=4 |Y|=2 且|X+Y|=X+Y 求X+Y 若x*x+y*y=x+y-1/2,求x,y的值如题 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 2x-y=2,求[(x²+y²)-(x-y)²+2y(x-y)]÷4y 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知2y-x=-3,求[4y(2x-y)-2x(2x-y)]/(2x-y 已知x/y=2,求2x(x+y)-y(x+y)/4x²-4xy+y² 若2x-3y=0,求5x+4y/3x-2y 若x^2+y^2-6x+4y+13=0 求x+y 因式分解 若 x^2+4x+y^2-6y+13=0 求y^x 若x y满足x^2+y^2-2x+4y=0求x-2y的最大值 若x^2+y^2+5/4=2x+y,求x^Y+y^x的值? RT,若（√2x-y）+y^2+4y+4=0,求[(x-y)^2+(x+y)(x-y)]÷2x的值 若x.y满足x^2+4x+y^2-10y+29=0.求x+y的值 若x*x-4y*y=-15,x+2y=3,求x和y的值 若(x-y)乘(x+y)=5,(x+y)^2=4,试求x-y的值 若实数x,y满足x²+y²-2x+4y=0,求x-y的最大值