[Maxima] simplification of (4-4*x^2)*sqrt(1-x^2)

[Barton Willis]

My understanding of Maple is poor, but I tried a few experiments with
Maple 10. OK:

  simplify((a*x^2-a) * sqrt(1-x^2)) --> -a * (1-x^2)^(3/2),

OK, but...

  simplify(42 + (a*x^2-a) * sqrt(1-x^2)) --> 42+(1-x^2)^
  (1/2)*a*x^2-(1-x^2)^(1/2)*a

For a naive Maple user (me), 42 + (a*x^2-a) * sqrt(1-x^2)) doesn't
automatically simplify to 42 - a * (1-x^2)^(3/2).

Barton