For a second-order linear homogeneous differential equation,
\[
y''+P(x)y'+Q(x)y=0,
\]
if one solution \(y_{1}\) is known, immediately use
\[
y_{2}=y_{1}\int
\frac{e^{-\int P(x)\,dx}}
{(y_{1})^{2}}\,dx.
\]
This formula is frequently used in university examinations and competitive exams for finding the second independent solution without solving the entire differential equation from scratch.