# How do you find the equation of a line with m=-4 and (3,0)?

Mar 30, 2018

$y = - 4 x + 12$

#### Explanation:

One way to write the equation of a line is in the slope-intercept form written like this:
$y = m x + b$
$\text{m=slope}$
$\text{b=y-intercept}$ (where the line crosses the $\text{y-axis}$)

$m = - 4$
$x = 3$
$y = 0$

Normally, the equation of a line is left with $x$ and $y$ being variables, and $m$ and $b$ having values . Since we do not have a value for $b$, we will plug all those numbers in and solve.

Substituting those in, the equation should look like this.

$0 = \left(- 4\right) \left(3\right) + b$

$0 = - 12 + b$

$12 = b$

So the equation of the line would be:
$y = - 4 x + 12$ graph{y = -4x + 12 [-17.13, 18.9, -2.64, 15.38]}
And this is your equation graphed. Notice how the line crosses the $\text{y-axis}$ at $12$, and that the slope is $- 4$, just like the equation says.