3.3.18 Not exact ode but can be made exact with integrating factor

ode internal name "exactWithIntegrationFactor"

This has the form \(M\left ( x,y\right ) +N\left ( x,y\right ) y^{\prime }=0\) where \(\frac {\partial M}{\partial y}\neq \frac {\partial N}{\partial x}\) where there exist integrating factor \(\mu \) such that \(\mu M\left ( x,y\right ) +\mu N\left ( x,y\right ) y^{\prime }=0\) becomes exact. Three methods are implemented to find the integrating factor.