\[ (-a-x) y(x)+4 x y''(x)=0 \] ✓ Mathematica : cpu = 0.0702304 (sec), leaf count = 78
DSolve[(-a - x)*y[x] + 4*x*Derivative[2][y][x] == 0,y[x],x]
\[\left \{\left \{y(x)\to \frac {1}{4} c_2 e^{-x/2} x \, _1F_1\left (\frac {1}{128} (-32 (-a-4 i)-128 i)+1;2;x\right )+\frac {1}{4} c_1 e^{-x/2} x U\left (\frac {1}{128} (-32 (-a-4 i)-128 i)+1,2,x\right )\right \}\right \}\] ✓ Maple : cpu = 0.039 (sec), leaf count = 21
dsolve(4*x*diff(diff(y(x),x),x)-(x+a)*y(x)=0,y(x))
\[y \left (x \right ) = c_{1} \WhittakerM \left (-\frac {a}{4}, \frac {1}{2}, x\right )+c_{2} \WhittakerW \left (-\frac {a}{4}, \frac {1}{2}, x\right )\]