9 Section 2.2.2, Equal roots, reduction of order. Page 147

  9.1 problem 1
  9.2 problem 2
  9.3 problem 3
  9.4 problem 4
  9.5 problem 6
  9.6 problem 7
  9.7 problem 10
  9.8 problem 11
  9.9 problem 12
  9.10 problem 13
  9.11 problem 14
  9.12 problem 15
  9.13 problem 16
  9.14 problem 19
  9.15 problem 20