Question

I have a first order differential equation (dq/dt) + 100q = 0.2, How do I find the integrating factor here?

Answer 1

this is already in standard form:\[q'+p(t)q=q(t)\]where p(t)=100 and q(t)=0.2
the integrating factor is found by:\[u(t)=e^{\int p(t)dt}\]

Answer 2

if the equation is of form y'+yP(x)= Q(x)

then Integrating factor = \[e ^{\int\limits_{?}^{?}P(x)dx}\]

so here in your equation

integrating factor = e^(100x)