The solution to y" = 0 is a straight line y = C + Dt. Convert to a matrix equation:
d/dt[y y'] =[0 1 ; 0 0] has the solution [y y'] = e ^At[y(0) y'(0)].
This matrix A cannot be diagonalized. Find A^2 and compute e^At = I + At + .5A^2t^2... Multiply your e^At times y(0), y'(0) to check the line y(t) = y(0) +y'(0)t
I'm not even sure what A is in this question...