1/3x+1/4y=16 1/3y+1/4x=19 帮我,+20.

{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 先化简 再求值 (2x-y)(y+x)-(x-2y)(2y+x)-(-3y+x)^2其(√x+1)+y^2+4=-4y 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 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 2(x-y)/3-(x+y)/4=-1 (1) 6(x+y)-4(2x-y)=16 (2) 3分之2(X-Y)-4分之X+Y=-1,3(X+Y)-2(X-Y)=16 解方程组2(x-y)/3-x+y/4=-1 6(x-y)-4(2x-y)=16 解方程组：2(x-y)/3-x+y/4=-1 ,6(x+y)-4(2x-y)=16 2(X-Y)/3=(X+Y)/4 -1 6(X+Y)=4(2X-Y)+16解方程 6(x+y)=4(2x-y)+16,2(x-y)/3=x+y/4-1 2(x-y)/3—x+y/4=1 6(x+y)—4(2x-y)=16 3分之2(x-y)-4分之x+y=-1 8(x+y)-4(2x-y)=16 (2x-2y)/3-(x-y)=-1和6(x+y)-4(2x-y)=16 初二上学期方程题 4x+y=5 5x+4y=63x-2y=1 2x+3y=13x-2y=7 7x+5y=32x+3y=17 2x-y=-4x+5y=6 2x+y=23x-6y=4 3x+2y=52x+y=73x-4y=53x+y=1x-2y=-1x+y=42x+3y=92x-3y=74x+5y=3x+y=20004x+6y=90003x+5y=113x-2y=42x+3y=215x-2y=5x+y=54x+3y=182x+3y=16x+4y=132x+3y=40x [(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y,其中x=1/2,y=1/3