How do you solve 2x = 4 and 2x – y = 5?

Aug 21, 2015

$\left\{\begin{matrix}x = 2 \\ y = - 1\end{matrix}\right.$

Explanation:

Notice that you can find the value of $x$ from the first equation by dividing both sides by $2$

$\frac{\textcolor{red}{\cancel{\textcolor{b l a c k}{2}}} \cdot x}{\textcolor{red}{\cancel{\textcolor{b l a c k}{2}}}} = \frac{4}{2}$

$x = \textcolor{g r e e n}{2}$

Now simply take this value of $x$ and plug it into the second equation. This will allow you to find the value of $y$

$2 x - y = 5$

$2 \cdot \left(2\right) - y = 5$

$4 - y = 5$

This is equivalent to

$y = 4 - 5 = \textcolor{g r e e n}{- 1}$