Solve the initial value problem yy' + x = + y with y(3) = -27. a. To solve this, we should use the substitution U= = dy Enter derivatives using prime notation (e.g., you would enter y for dz ). b. After the substitution from the previous part, we obtain the following linear differential equation in a, u, u'. c. The solution to the original initial value problem is described by the following equation in z, y.