Question

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

Answer 1

`y = -4x + 12`

Explanation:

One way to write the equation of a line is in the slope-intercept form written like this:
`y = mx + b`
`"m=slope"`
`"b=y-intercept"` (where the line crosses the `"y-axis"`)

The problem has already given
`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 = (-4)(3) + b`

`0 = -12 + b`

`12 = b`

So the equation of the line would be:
`y = -4x + 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 `"y-axis"` at `12`, and that the slope is `-4`, just like the equation says.