How do you simplify (9-5i)(7+4i)?

Feb 2, 2017

Solve as normal, then replace the $i$s

Explanation:

Foil
$= 63 + 36 i - 35 i - 20 {i}^{2}$

Combine Like Terms
$= 63 + i - 20 {i}^{2}$

Substitute in ${i}^{2} = - 1$
$= 63 + i + 20$

$83 + i$