Work Step by Step
RECALL: (1) $(a+b)(a-b) = a^2-b^2$ (2) $i^2=-1$ Use rule (1) above to obtain: $=(-7)^2 - i^2 \\=49 - i^2$ Use rule (2) above to obtain: $=49-(-1) \\=49+1 \\=50$
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