I need to find the Vandermonde determinate of the following:

V4 =
| 1 a a2 a3 |
| 1 b b2 b3|
| 1 c c2 c3 |
| 1 x x2 x3|

(-1)R1 + R2 ↔ R2
(-1)R1 + R3 ↔ R3
(-1)R1 + R4 ↔ R4

| 1 a a2 a3 |
| 0 (b-a) (b-a)(b+a) (b3-a3)|
| 0 (c-a) (c-a)(c+a) (c3-a3)|
| 0 (x-a) (x-a)(x+a) (x3-a3)|

Now I don't know what to do. Any help would be great.