You'll want to use the quadratic formula:
-b (+/-) sqrt(b^2 - 4ac), all divided by 2a.
Under the square root you'll get:
-11
remember that the square root of -1 is i.
sqrt(-11) can be factored to sqrt(11*-1) and then sqrt(-1) * sqrt(11)
which becomes i*sqrt(11)
so your complex solution is:
-3 (+/-) (i*sqrt(11)), all over 4
