# How do you multiply -5(a-2b) ?

Jul 10, 2016

$- 5 \left(a - 2 b\right) = - 5 a + 10 b$

#### Explanation:

$\textcolor{b l u e}{\text{The teaching bit}}$

The purpose of the brackets in this question is to group things.

Let me demonstrate:

Consider $3 \times 5 = 15$

This is $5 + 5 + 5 \leftarrow \text{ Three lots of 5 all put together}$
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But 5 can be written in many ways. Suppose we write 5 as 4 + 1

The $3 \times 5$ is exactly the same as $3 \times \left(4 + 1\right)$

So we have 3 lots of $\left(4 + 1\right)$ giving

$\left(4 + 1\right) + \left(4 + 1\right) + \left(4 + 1\right)$

$4 + 4 + 4 \text{ } + 1 + 1 + 1$

Observe that we have 3 lots of everything inside the brackets.
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$\textcolor{b l u e}{\text{Answering you question}}$

$- 5 \left(a - 2 b\right) = - 5 a + 10 b$