dy/dx=2(y/x)/(3-(y/x)²)令u=y/x，dy/dx=u+xdu/dxxdu/dx=2u/(3-u²)-u(3-u²)/(u³-u)du=dx/x1/(u-1)-3/u+1/(u+1)du=lnx+lnC(u²-1)/u³=Cx(y²x-x³)/y³=Cxy²-x²=Cy³
（3x²-y²）y'=2xy
