Question

Y’＋Y=3X求微分方程通解

Answer 1

y'+y=3x

设3x-y=u

dy=d3x-du

dy/dx+y=3x

3-du/dx=u

du/(3-u)=dx

ln|u-3|=-x+C0

u-3=Ce^(-x)

u=Ce^(-x)+3

通解y=3x-Ce^(-x)-3