3X+7Y=10 y=1 x=
{ x-y/7-x+y/10=1/2 {2(x-y)+5(x+y)=3
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
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
y'=(x-y+1)/(x+y-3)通解
x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9
若x、y满足2x+y=6,x-3y=1,求7y(x-3y)²-2(3y-x)³的值
X+Y=7(100X+Y)-(10Y+X)=(10Y+X)-(10X+Y)
2(x+y) 3x+3y=24 x+y/2x x y/2y= 1