9 The first, second and third terms of a geometric progression are \(3 k , 5 k - 6\) and \(6 k - 4\), respectively.
- Show that \(k\) satisfies the equation \(7 k ^ { 2 } - 48 k + 36 = 0\).
- Find, showing all necessary working, the exact values of the common ratio corresponding to each of the possible values of \(k\).
- One of these ratios gives a progression which is convergent. Find the sum to infinity.