4x^2-28x+y^2+6y+58=0,求3x-2y.

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4x^2-28x+y^2+6y+58=0
4x^2-28x+49+y^2+6y+9=0
(2x-7)^2+(y+3)^2=0
(2x-7)^2=0,(y+3)^2=0
x=7/2
y=-3
3x-2y
=3*7/2-2*(-3)
=21/2+6
=33/2

4x^2-28x+y^2+6y+58=0,求3x-2y. 已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)} 已知x*x-4xy+4y*y=0 求[2x(x+y)-y(x+y)]/(4x*x-4xy+y*y)的值? 已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 已知x^3+xy^2+x+x^2y+y^3+y=0,求5x-6y/3x+4y的值. 已知x.x+y.y+8x+6y+25=0,求代数式(x.x-4y.y)/(x.x+4xy+4y.y)-x/(x+2y)的 {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 求x+y/3+x-y/2=6 3(x+y)-2(x-y)=28方程组的解