Question: how do i use Maple to solve for "a" help~~

eqn :=-p*(l^2-a^2)^(3/2)+a^3*q; l is letter not number if want to find a .....a =??......plz use maple to find the answer i use hand to do it, so the answer is a = (p^(1/3)*l)/sqrt(p^(2/3)+q^(2/3)); but i use Maple it gave me different answer.... so plz help!
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