# How do you solve the simultaneous equations 4x + y = -1 and 4x - 3y = 7?

May 20, 2018

$x = \frac{1}{4} \mathmr{and} y = - 2$

#### Explanation:

$4 x + y = - 1 - - - e q n 1$

$4 x - 3 y = 7 - - - e q n 2$

Subtracting $e q n 2$ from $e q n 1$

$\left(4 x - 4 x\right) + \left(y - \left(- 3 y\right)\right) = - 1 - 7$

$0 + y + 3 y = - 8$

$4 y = - 8$

$y = - \frac{8}{4}$

$y = - 2$

Substiting the value of $y$ into $e q n 1$

$4 x + y = - 1 - - - e q n 1$

$4 x + \left(- 2\right) = - 1$

$4 x - 2 = - 1$

$4 x = - 1 + 2$

$4 x = 1$

$x = \frac{1}{4}$

Therefore;

$x = \frac{1}{4} \mathmr{and} y = - 2$