Question: ShowSolution does not compute the indeterminate limit infinity minus infinity in some cases

In the following I show two functions f and g where ShowSolution(Limit(..)) works for f but not for g. Any idea why?


f := x^2 + x:
limit(f, x = -infinity);
ShowSolution(Limit(f, x = -infinity), maxsteps = 100);
// step-by-step solution is produced

g := x^2 + 3*x:
limit(g, x = -infinity);
ShowSolution(Limit(g, x = -infinity), maxsteps = 100);
Error, (in Student:-Calculus1:-ShowSolution) unable to compute solution steps

Maple is able to change f into an equivalent expression by factoring out x^2, but does not seem to be able to do it with g.

I attach two screenshots that show this curious behaviour.

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