已知x^2-y^2=45 x+y=9,求X-y的值

已知x^2-y^2=45 x+y=9,求X-y的值 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x-y=3,求[（x+y)(x-y)-(x-y)^2+2y(x-y)]除以的值 已知3x =2y 求x/x+y+y/x-y-y²/x²-y² 已知|x|=2,|y|=3,|x+y|=-(x+y)求x-y 已知x≠y,x^2-x=y^2-y,求x+y的值. 已知（x+y+2)(x+y-2)=45,求x+y的值 已知x^2-6xy+9y^2=0,求(x-y)/(x+y) 已知,X:Y=3:2,求代数式4X-9Y:2X+3Y 已知x/y=3/2求代数式4x-9y/2x+3y 已知(x+y)(x+y-6)+9=0求2(x+y)的值 已知:(x+y)(x+y+6)+9=0 求2(x+y)的值 已知2x-y/x+2y=3,求2(2x-y)/x+2y-9(x+2y)/2x-y+3的值. 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 已知：x+9y=y-3x,求(x^2-y^2)/(x^2+y^2)的值RT 已知方程组{2x+y=6 x+2y=9},求x+y与x-y的值 已知x+y=9,x-y=6,求x²-y²-2x-2y的值