5x=y,5:y=x,3x=4y,3:x=4:y,3;x=y:4,3x+4x=y,3x+4=y y和x成比例吗

5x=y,5:y=x,3x=4y,3:x=4:y,3;x=y:4,3x+4x=y,3x+4=y y和x成比例吗 （5x+3y)(3y-5x)-(4x-y)(4y+x)= 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 xy=1,x与y成( )比例,x=y/5,x与y成( )比例,x/3=y/4,x与y成( )比例,3/x=y,x与y成( 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-( 数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y {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/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6