g: [3, -2, 2] + t·[1, -1, 2] = [t + 3, -t - 2, 2·t + 2]
([t + 3, -t - 2, 2·t + 2] - [-1, 2, 1])^2 = ([t + 3, -t - 2, 2·t + 2] - [3, 4, -7])^2
([t + 4, -t - 4, 2·t + 1])^2 = ([t, -t - 6, 2·t + 9])^2
6·t^2 + 20·t + 33 = 6·t^2 + 48·t + 117
- 28·t - 84 = 0
t = -3
g: [(-3) + 3, -(-3) - 2, 2·(-3) + 2] = [0, 1, -4]