Question number $3.$

The function

$y=C_1{e}^{3x}+C_2{e}^{-x}$

is the general solution of

$y^{\text{'}\text{'}}-3y^{\text{'}}-y=0$

$y^{\text{'}\text{'}}+2y^{\text{'}}-3y=0$

$y^{\text{'}\text{'}}+3y^{\text{'}}+3y=0$

$y^{\text{'}}+2y=0$

$y^{\text{'}\text{'}}-2y^{\text{'}}-3y=0$

None of the above.