The slope of the line is is (2 - 1.2)/(5 - 1) = 1/4.
Then by point slope form, the equation of the line is
y - 2 = 1/4(x - 5)
y - 2 = 1/4*x - 5/4
y = 1/4*x + 3/4
I'm going to suggest using y = mx + b.
Finding the slope: By observation, we can take a shortcut, by noting
that the line goes vertically 2 for horizontally 10.
That makes the slope 0.2.
(2 – 0)
Or more formally m = ––––———
(5 – (–5))
And from the graph, the y-intercept is 1.
Put them together and we've got y = 0.2x + 1
.
