x^2+y^2=15,x+y=7,x＞y,求x-y
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x^2+y^2=15,x+y=7,x＞y,求x-yx^2+y^2=15,x+y=7,x＞y,求x-yx^2+y^2=15,x+y=7,x＞y,求x-y(x-y)^2=(x^2+y^2)-2xy=(x^
x^2+y^2=15,x+y=7,x＞y,求x-y
x^2+y^2=15,x+y=7,x＞y,求x-y
x^2+y^2=15,x+y=7,x＞y,求x-y
(x-y)^2=(x^2+y^2)-2xy
=(x^2+y^2)-[(x+y)^2-(x^2+y^2)]
=2(x^2+y^2)-(x+y)^2
=2*15-7^2=-19
x+y=7得 （x+y）^2=x^2+y^2+2*x*y=49 又x^2+y^2=15,两式相减，x*y=17,
(x-y)^2=x^2+y^2-2*x*y=15-34=-19???接下来就不知道了
x^2+y^2=15,x+y=7,x＞y,求x-y
x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2
x+2y=2x+y+1=7x-y 求：2x-y?
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
2（x+y)-3(x-y)=3 ,4(x+y)+3(x-y)=15
{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
填空：x-y/x+y=( )/x^2-y^2
（x-y)2•(y-x)³(x-y)=?
(x-y)(x-2y)+(x-2y)(x-7y),其中X=4,Y=1.5
y+y'-2y=2x
微分方程y - 2y' + y = x
(x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)=
(x+y)(x-y)+(x-y)平方-(x-y)(3x-y) 其中x=-2 y=3分之一
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
(x-4y)(2x+y)=
(x+y)(2x-3y)=?