solve y''-4y'+13y=0 if y(0)= -1 and y'(0)= 2.

from my lecture notes im confused about this step

general solution (alpha=2, beta=3)

y=Ae^[(2+3i)x] + Be^[(2-3i)x]

y=C(a small 1 at the corner)(e^2x)cos3x + C(a small 2 at the corner)(e^2x)sin3x

how to get from the first step to the second step? someone please explain to me thanks =)