y: cost
x: number of days
the following points are on the line (30, 1200) and (60, 1500)
The slope of a line given two points (x1, y1) and (x2, y2) is computed as follows:
Replacing with (30, 1200) and (60, 1500), we get:
The slope-intercept form of a line is:
y = mx + b
where m is the slope and b the y-intercept.
Replacing with point (30, 1200) and m = 10, we get:
1200 = 10(30) + b
1200 = 300 + b
1200 - 300 = b
900 = b
Then, the equation is:
y = 10x + 900