Here's a graph of a linear function. Write the equation that describes that function. Express it in slope-intercept form
Well, as you can see, the function is a line
y = mx + b is slope intercept form of a line m = slope b = y axis intercept (when x = 0)
Find two 'convenient' points like -3,2 and 0,-4
calculate the slope, m as (y1-y2) / (x1-x2)
you will then have y = mx + b
then put one of the points into your building equation to calculate 'b'
(BTW you can 'see' 'b' where x = 0 the value of b is shown as -4 on the graph)