4x-3y+1=0 3x+2y-12=0

已知实数x,y满足{x≧0 y≧x 4x+3y≦12}.z=2y+3/x+1 的取值范围 微分方程(1)(y'')^2+5y'-y+x=0;(2)y''+5y'+4y^2-8x=0;(3)(3x+2y)dx+( 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 已知X,Y,满足(X+3Y)(X-3Y)=-10(Y^2-6/5)和2X(Y-1)+4(1/2X-1)=0 （1）y+3x+17=0 5y-2x+17=0 （2）x+y+z=12 x+2y+5z=22 x=4y （3）x+y+z x>1,y>0,且满足xy=x^y,x/y=x^3y,求x+y 若x^5+x^4y+x^4+x+y+1=0,且3x+2y=1,求x,y的值 {4x-3y-10=0 3x-2y=0,{3x-4(x-y)=2 2x-3y=1,{2(x+y)-(x-y)=3 (x+ 若3x-4y=0,则x/y=______,（x-y)/y=______,（3x+2y)/(2x+3y)=_____. 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1