Answer
$(3-7i)^{2}$ = $-40-42i$
Work Step by Step
1. $(3-7i)^{2}$
2. Multiply $(3-7i)\times(3-7i)$ (use the FOIL method to distribute the First, Outer, Inner, and Last terms): $9-21i-21i+49i^{2}$
3. Combine like terms: $9-42i+49i^{2}$
4. Change $49i^{2}$ to -49 because $i^{2} = -1$ and $49\times-1 = -49$ : $9-42i-49$
5. Combine like terms:$-40-42i$
