Linear Equations
We typically write linear equations in slope-intercept form:
[tex]y=mx+b[/tex]
- m = slope
- b = y-intercept (the value of y when x=0)
Because this graph has a proportional relationship, it means that they pass through the point (0,0), and that our y-intercept is 0. Our equation looks like this:
[tex]y=mx[/tex]
Solving the Question
First, we typically find the slope of the equation using the slope formula:
[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex] where [tex](x_1,y_1)[/tex] and [tex](x_2,y_2)[/tex] are two points that fall on the line
⇒ Plug in any two points that the line passes through, such as (0,0) and (3,12):
[tex]m=\dfrac{12-0}{3-0}\\\\m=\dfrac{12}{3}\\\\m=4[/tex]
Therefore, the slope of the line is 4. Plug this into [tex]y=mx[/tex]:
[tex]y=4x[/tex]
Answer
[tex]y=4x[/tex]