（x+y)^2=11,(x-y)^2=7,求xy的值

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+2y=2x+y+1=7x-y 求：2x-y? 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7 x^2+y^2=15,x+y=7,x＞y,求x-y {6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1 当x+y=2时7(x+y)一(x+y)+(x+y)=? 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 (x-y)(x-2y)+(x-2y)(x-7y),其中X=4,Y=1.5 大括号x+y/2+x-y/3=11/6 4(x+y)-5(x-y)=7 快 7x+3y=44,11x+2y=61,求x,y 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 填空：x-y/x+y=( )/x^2-y^2 （x-y)2•(y-x)³(x-y)=? y+y'-2y=2x 微分方程y - 2y' + y = x