We want to expand
[tex](8+5i)(7+2i)[/tex]Using the distributive property, we have
[tex]\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}[/tex]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.
