# How do you solve x+3y=-1, y=x+1?

Mar 3, 2018

For a problem like this you would use substitution method.

#### Explanation:

Since the problem already gives you the value of $y$ (which is $x + 1$), you would use that information and apply it to the equation

$x + 3 y = - 1$

How you would do this is by replacing $x + 1$ (the value of $y$) into the original equation wherever you see $y$.

So:

$x + 3 y = - 1$

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

(Solve algebraically)

$x + 3 x + 3 = - 1$

$4 x + 3 = - 1$

$4 x = - 4$

$x = - 1$

Now to find $y$ as a number, you would plug in $- 1$ as $x$ and solve:

$y = x + 1$

$y = - 1 + 1$

$y = 0$