# How do you simplify -10i(4+7i) and write the complex number in standard form?

Aug 10, 2018

$70 - 40 i$

#### Explanation:

$- 10 i \left(4 + 7 i\right)$

First, we know that standard form is $a + b i$.

Distribute the $- 10 i$:
$- 40 i - 70 {i}^{2}$

We know that ${i}^{2}$ equals to $- 1$, so
$- 40 i - 70 \left(- 1\right)$

$- 40 i + 70$

Put it in the form $a + b i$:
$70 - 40 i$

Hope this helps!