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Worked Example

Compute (2 + i)(1 − i)

Standard FOIL — same as algebra, just remember $i^{2} = -1$ at the end.

Step-by-step solution

(2 + i)(1 - i)FOIL
= 2 - 2i + i - i^{2}Distribute all four products
= 2 - i - (-1)Use $i^{2} = -1$
= 3 - i✓ Final answer