What is an equivalent form of \( (3-7 i)^{2} \) ?

Step 1 ：\((3-7i)^2\)

Step 2 ：\(3^2 + 2(3)(-7i) + (-7i)^2\)

Step 3 ：\(9 - 42i + 49i^2\)

Step 4 ：\(9 - 42i - 49\)

Step 5 ：\(-40 - 42i\)