I'm not sure where to start with these questions. I know this might have to do with variation of parameters or Cauchy-Euler Equation but I'm still not sure.

Q5 (10 points) (a) The roots of a quadratic polynomial are m1 = 1 + i and m2 = 1 - i. Write the polynomial in the form m2 + bm + c, i.e. determine the values of b and c. Hint: Check your answer by finding the roots of your polynomial and recovering m, and m2. (b) Write down a linear fifth-order differential equation whose general solution is u = 1+ cox + ce + c4e cos x + ce sin x