How do you solve the following system?: 4x-y=-1 , 4x-3y=15

Dec 23, 2015

The solution for the system of equations is
color(blue)(x=-9/4,y=-8

Explanation:

$\textcolor{b l u e}{4 x} - y = - 1$.......equation $\left(1\right)$

$\textcolor{b l u e}{4 x} - 3 y = 15$.........equation $\left(2\right)$

Solving by elimination

Subtracting equation $2$ from $1$

$\cancel{\textcolor{b l u e}{4 x}} - y = - 1$
$\cancel{- \textcolor{b l u e}{4 x}} + 3 y = - 15$

$2 y = - 16$

$y = \frac{- 16}{2}$

color(blue)(y=-8

Finding $x$ by substituting $y$ in equation $1$:
$4 x - y = - 1$

$4 x = - 1 + y$

$4 x = - 1 - 8$

$4 x = - 9$

color(blue)(x=-9/4