[[_2nd_order, _with_linear_symmetries]]
Book solution method
TO DO
Mathematica ✗
cpu = 0.954187 (sec), leaf count = 0 , DifferentialRoot result
Maple ✓
cpu = 0.184 (sec), leaf count = 46
DSolve[(a + b*x)*y[x] + 2*(1 - 3*x)*(1 - x)*y'[x] + 4*(1 - x)*x*y''[x] == 0,y[x],x]
Mathematica raw output
{{y[x] -> DifferentialRoot[Function[{\[FormalY], \[FormalX]}, {(-a - \[FormalX]*
b)*\[FormalY][\[FormalX]] + (-2 + 8*\[FormalX] - 6*\[FormalX]^2)*Derivative[1][\
[FormalY]][\[FormalX]] + 4*(-1 + \[FormalX])*\[FormalX]*Derivative[2][\[FormalY]
][\[FormalX]] == 0, \[FormalY][2] == C[1], Derivative[1][\[FormalY]][2] == C[2]}
], Function[\[FormalX], {{Re[\[FormalX]] <= 0, Im[\[FormalX]] == 0}}]][x]}}
Maple raw input
dsolve(4*x*(1-x)*diff(diff(y(x),x),x)+2*(1-x)*(1-3*x)*diff(y(x),x)+(b*x+a)*y(x) = 0, y(x),'implicit')
Maple raw output
y(x) = (-1+x)*(_C2*HeunC(-3/2,1/2,1,3/8-1/4*b,1/8-1/4*a,x)*x^(1/2)+_C1*HeunC(-3/
2,-1/2,1,3/8-1/4*b,1/8-1/4*a,x))