Find all zeros of the function f(x) =x3+9x.
x=0, 3, -3
x=3i, 0, 3
x=3, -3i, 0
x=0, -3i, 3i
f(x)=x3+9x
f(x)=x(x2+9)=x(x-3i)(x+3i)
zeroes are x=0, 3i, -3i