assuming that you are dealing with the series y= ao + a1x +a2x2 + a3x3 + ...............
then y(o) = ao and from your initial conditions, y(0) = -1 so, ao = -1
when you differentiate y'(x) = a1 + 2a2x + 3a3x2 + ............................
then y'(0) = a1 and from your initial conditions y'(0) = 2 so, a1 = 2