Question

How do you graph `y=1/4x-1` using slope intercept form?

Answer 1

A line passing through `(0,-1)` and `(4,0)`

graph{1/4x-1 [-7.82, 12.18, -4.6, 5.4]}

Explanation:

We need to find two points, then join up the line. The natural points to go for are those on the x-axis and the y-axis.

To find the point where it crosse the y-axis:

Let `x=0`
`y=1/4(0)-1`
`y=-1`
`:.` crosses at `(0,-1)`

You can also tell this from the value of `c` from the general equation `y=mx+c`, as, if `x=0, y=c` Since `c=-1`, it passes through `(0,-1)`, although I'd say its more formal to go through the algebra.

Now to find where it crosses the x-axis:

Let `y=0`
`0=1/4x-1`
`1=1/4x`
`x=4`
`:.` crosses at `(4,0)`

We can now join up these two points like so:

graph{1/4x-1 [-7.82, 12.18, -4.6, 5.4]}