微分方程dy/dx=x/y+k怎么求解?
2个回答

令y/x=u y=ux y'=u+xu'

代入原式得:u+u'x=1/u+k

u'x=1/u+k-u

du/(1/u+k-u)=dx

udu/(1+ku-u^2)=dx

(2u-k+k)du/(1+ku-u^2)=2dx

(2u-k)du/(1+ku-u^2)+kdu/(1+ku-u^2)=2dx

两边积分得:

-ln|1+ku-u^2|+∫kdu/(1+k^2/4-(u-k/2)^2)=x^2

通解为:-ln|1+ku-u^2|+(2k/√(4+k^2)ln|(u-k/2+√(4+k^2)/2)/(u-k/2-√(4+k^2)/2)|=x^2+C

其中u=y/x