{1/2x — 4y=30{y — 2x=15用代入法解

3(x+y)—4(x—y)=4 { (x+y)/2+(x—y)/6=1 2(x-y)/3—x+y/4=1 6(x+y)—4(2x-y)=16 [(x/x-y) -1]/(y的平方/x+y)乘以(x-x的平方/x+y),其中x=—2,y=—1. {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 3(x+y)—4(x-y)=4,(x+y/2)+(x-y/6)=1.解方程组 化简1— x-y/x+2y÷x²-y²/x²+4xy+4y² 已知X+Y=4018,X—Y=1/2,则-X*X+Y*Y的值为? 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知:【(x²+y²)-(x-y)²+2y(x-y)】/4y=1,求4x/4x²-y²-1/2x+y 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 2x—3y+5=0 3x+2y=12 y=2x 7x—3y=4 Y+1=三分之x+1 2x—3y=1 方程组 (x-4y)(2x+y)= X的平方+Y的平方+2X—4Y+5=0,求X+Y=什么X^2+Y^2+2X-4Y+5=0 怎么变为(X+1)^2+(Y-2)^2=0