How do you multiply $(2+i)(2-3i)$ in trigonometric form?

Question

1793 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-10-21T17:13:59

$7-4i$

First, we have to know that
$i^1=i$
$i^2=-1$
$i^3=-i$
$i^4=1$

Then, we can expend the expression and simplify it with the above rule:

$(2+i)(2-3i)$
$=4-6i+2i-3i^2$
$=4-4i-3i^2$
$=4-4i-3(-1)$
$=4-4i+3$
$=7-4i$

It's the answer! Hope it can help you :)

How do you multiply (2+i)(2-3i) (2+i)(2-3i) in trigonometric form?