(3х-1)2

It depends on the intended meaning:

• If you mean 2(3x − 1), then the simplification is 6x − 2. Steps: 2 × 3x = 6x, 2 × (−1) = −2 → 6x − 2.

• If you mean (3x − 1)² (i.e., the square), then it expands to 9x² − 6x + 1. Steps: (3x)² − 2·(3x)·1 + 1² = 9x² − 6x + 1.

Which one did you intend? If you meant something else, tell me and I’ll adjust.