If your 4x2 matrix is A, have you considered multiplying from the left with ?
Find the Least-squares Solution z of the Overdetermined System
|-3 1 | | 70 |
| 1 1 | x = | 21 |
|-7 1 | | 110 |
| 5 1 | |-35 |
Excuse my poorly typed notation as that is supposed to be a matrix times x = another matrix.