How do you solve 2x + y = 7 and 4x - y = 23 ?

Mar 6, 2016

$x , y = 5 , - 3$

Explanation:

color(blue)(1) )color(blue)(2x+y=7

color(blue)(2))color(blue)(4x-y=23

We can eliminate $y$ from the first equation by $- y$ in the second equation

Add both of the equations

$\rightarrow \left(2 x + y = 7\right) + \left(4 x - y = 23\right)$

$\rightarrow 6 x = 30$

color(green)(rArrx=30/6=5

Now substitute the value of $x$ to the first equation

$\rightarrow 2 \left(5\right) + y = 7$

$\rightarrow 10 + y = 7$

color(green)(rArry=7-10=-3