Subjects algebra

Complex Multiplication 22D88F

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Question: Simplify the expression to a + bi form: $(-4 - 5i)(9 + 2i)$
1. **State the problem:** Simplify the expression $(-4 - 5i)(9 + 2i)$ into the form $a + bi$ where $a$ and $b$ are real numbers. 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:** $$ (-4 - 5i)(9 + 2i) = (-4)(9) + (-4)(2i) + (-5i)(9) + (-5i)(2i) $$ 4. **Calculate each term:** $$ = -36 - 8i - 45i - 10i^2 $$ 5. **Simplify $i^2$ term:** Since $i^2 = -1$, $$ -10i^2 = -10(-1) = 10 $$ 6. **Combine like terms:** $$ -36 + 10 - 8i - 45i = (-36 + 10) + (-8i - 45i) = -26 - 53i $$ 7. **Final answer:** The expression simplifies to $$ \boxed{-26 - 53i} $$