Question

Error AnalysisFind the error in the arithmetic below. Explain what is incorrect andredo the problem correctly.(8 + 5i)(7 + 2i) = 56 + 16i + 35i + 10i = 56 + 51i

Answer 1

We want to expand

`(8+5i)(7+2i)`

Using the distributive property, we have

`\begin{gathered} (8+5i)(7+2i)=8(7+2i)+5i(7+2i) \\ =56+16i+35i+10i^2 \\ =56+51i+10(-1) \\ =56+51i-10 \\ =46+51i \end{gathered}`

What was incorrect in the equation given in the problem is the last term after expanding the product. 2i times 5i is -10, not 10i.