Transient analysis with differential equation
Kirchoff's voltage law: $$\large 20\int (3-i)dt+10(3-i)=4i+ 2\large\frac{di}{dt}$$

Differentiating: $$\large 60-20i-10\large\frac{di}{dt}=4\frac{di}{dt}+2\frac{d^2i}{dt^2}$$

Homogeneous equation is: $$\large p^2 + 7p + 10=0$$