Subjects algebra

Complex Multiplication 45F4A4

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Question: Multiply. $(5 + 7i)(8 - 2i) = [blank] + [blank] i$ (Simplify your answer. Type integers. Do not factor.)
1. **State the problem:** Multiply the complex numbers $5 + 7i$ and $8 - 2i$. 2. **Recall the formula:** To multiply two complex numbers $(a + bi)(c + di)$, use the distributive property: $$ (a + bi)(c + di) = ac + adi + bci + bdi^2 $$ Remember that $i^2 = -1$. 3. **Apply the formula:** $$ (5 + 7i)(8 - 2i) = 5 \times 8 + 5 \times (-2i) + 7i \times 8 + 7i \times (-2i) $$ 4. **Calculate each term:** $$ = 40 - 10i + 56i - 14i^2 $$ 5. **Simplify $i^2$ term:** Since $i^2 = -1$, $$ -14i^2 = -14 \times (-1) = 14 $$ 6. **Combine like terms:** $$ 40 + 14 + (-10i + 56i) = 54 + 46i $$ 7. **Final answer:** $$ (5 + 7i)(8 - 2i) = 54 + 46i $$