\[ a y(x)+c \left (-e^{b x}\right )+y'(x)=0 \] ✓ Mathematica : cpu = 0.0265868 (sec), leaf count = 34
\[\left \{\left \{y(x)\to \frac {c e^{x (a+b)-a x}}{a+b}+c_1 e^{-a x}\right \}\right \}\]
✓ Maple : cpu = 0.013 (sec), leaf count = 25
\[ \left \{ y \left ( x \right ) = \left ( {\frac {c{{\rm e}^{ \left ( a+b \right ) x}}}{a+b}}+{\it \_C1} \right ) {{\rm e}^{-ax}} \right \} \]