0.5(X+Y)=400,4(X-Y)=400,是二元一次方程,怎么解

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 化简 x / y(x+y) - y / x(x+y) = 7x:4y,x:y=( ):( (x-4y)(2x+y)= 5x-4y(y-x)=? 已知x+y=-4试计算多项式0.5(x+y)+4(x-y)-3(x-y)-1.5(x+y)-x+y的值 x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x+x+x+y=60 .x-y=4 matlab画二元函数图像z = (x/(x+y) + 1.96*1.96/(2*(x+y)) - 1.96 * ((x/(x+y)*(1-x/(x+y))+1.96*1.96/(4*(x+y)))/(x+y))^0.5)/(1+1.96*1.96/(x+y))该怎么画 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? x+x+y+y+y=21 ,x+x+y+y+y+y+y=27 ,x ,y=? y=x(x 3X+X=( ) Y+4Y-3Y=( ) x+y／y=5／4,则x／y=---------------- x*x+2x+y*y-4y+5=0 x= y= 如果|X|=4 |Y|=2 且|X+Y|=X+Y 求X+Y