(1/2y+ )( +3x)=9x^2-1/4y^2(1/2y+_______ )( _________+3x)=9x^2-1/4y^2

9y=3x-(x-1),4(x+y)-(2x+4)=8y 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 变量x,y满足约束条件,x+y>=3,x-y>=-1,2x-y (x-y)^2+(x+y)(x-y) 其中 X =3 Y=-1 (x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2 函数,y=3x/(x^2+x+1) ,x 函数y=3x/(x^2+x+1) （x 解方程组 3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1 解方程组:{3(x+y)-2(x-y)=9,5(x+y)+2(x-y)=-1} 解二元一次方程 {3(x+y)-4(x-y)=-9 x+y/2+x-y/6=1 先化简再求值 x(9x-y)-y(y-x)+(x-y)的平方,其中x=-1,y=2