How do you simplify $(5-7i)(-4-3i)$ ?

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Answer 1 · 2018-08-10T17:54:06

$-41 + 13i$

$(5-7i)(-4-3i)$

Use FOIL to distribute:
$5 * -4 = -20$

$5 * -3i = -15i$

$-7i * -4 = 28i$

$-7i * -3i = 21i^2$

Combine them all together:
$-20 - 15i + 28i + 21i^2$

Combine like therms:
$-20 + 13i + 21i^2$

We know that $i^2 = -1$ , so:
$-20 + 13i + 21(-1)$

$-20 + 13i - 21$

$-41 + 13i$

Hope this helps!

How do you simplify (5-7i)(-4-3i)(5-7i)(-4-3i)?