how do you solve 2x^2+x^3=96?

x^3 + 2x^2 - 96 = 0

tried x = 1,2,3,4 and x=4 worked
by synthetic division
x^3 + 2x^2 - 96 = 0
(x-4)(x^2 + 6x + 24) = 0

solving x^2 + 6x + 9 = -24 + 9
(x+3)^2 = -15
x = +3 ± √15 i

x = 4 , 3 ± √15 i