Question

How do you graph `3x+y=15`?

Answer 1

Find two pair of sample solution points (the intercepts are often convenient);
Plot the two points;
Draw a straight line through the points.
`color(white)("XXX")`(see below)

Explanation:

Given `3x+y=15`

If `x=0`
then `y=15`

If `y=0`
then `x=5`

So we have two sample points `(0,15)` and `(5,0)`

Since `3x+y=15` is a linear equation, we only need two points to establish the graph.

Plotting these points and drawing a line through them gives us a graph that should look like: