(3x+5y)dx+(4x+6y)dy=0请不要粘贴网上的答案,那些我都看过了,没有帮助

2024-12-02 18:32:23
推荐回答(1个)
回答1:

解:∵设y=xt,则dy=xdt+tdx
代入原方程,得
(3x+5xt)dx+(4x+6xt)(xdt+tdx)=0
==>3x(2t^2+3t+1)dx+2x^2(3t+2)dt=0
==>3dx/x+2(3t+2)dt/(2t^2+3t+1)=0
==>3dx/x+[2/(2t+1)+2/(t+1)]dt=0
==>3ln│x│+ln│2t+1│+2ln│t+1│=ln│C│ (C是积分常数)
==>x^3(2t+1)(t+1)^2=C
==>x^3(2y/x+1)(y/x+1)^2=C
==>(2y+x)(y+x)^2=C
∴原方程的通解是(2y+x)(y+x)^2=C。