\( y^{\prime \prime}-y=0 \)
\(y(x) = c_1 \mathrm{e}^x + c_2 \mathrm{e}^{-x}\)
Step 1 :\(y^{\prime\prime}(x) - y(x) = 0\)
Step 2 :\(y(x) = c_1 \mathrm{e}^x + c_2 \mathrm{e}^{-x}\)