Chapter 7 - Section 7.7 - Complex Numbers - 7.7 Exercises: 49

$-16$

Work Step by Step

$\bf{\text{Solution Outline:}}$ To simplify the given expression, $(-8i)(-2i) ,$ multiply the numerical coefficients and multiply the $i$'s as if it were a literal coefficient. Then use $i^2=-1$. $\bf{\text{Solution Details:}}$ Multiplying the numerical coefficients and the $i$'s result to \begin{array}{l}\require{cancel} (-8\cdot-2)(i\cdot i) \\\\= 16i^2 .\end{array} Since $i^2=-1,$ the expression above is equivalent to \begin{array}{l}\require{cancel} 16(-1) \\\\= -16 .\end{array}

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