How to write a equation using a table

Example 1 :  Elizabeth’s cell phone plan lets her choose how many minutes are included each month. The table shows the plan’s monthly cost y for a given number of included minutes x. Write an equation in slope-intercept form to represent the situation.

Step 1 :  Notice that the change in cost is the same for each increase of 100 minutes. So, the relationship is linear.

Step 2 :  Choose any two points in the form (x, y), from the table to find the slope :

For example, let us choose (100, 14) and (200, 20).

Use the slope formula.

m  =  (y2 - y1) / (x2 - x1)

Substitute (100, 14) for (x1, y1) and (200, 20) for (x2, y2).

m  =  (20 - 14) / (200 - 100)

m  =  6 / 100

m  =  0.06

Step 3 :

Find the y-intercept using the slope and any point from the table.

Slope-intercept form equation of a line :

y  =  mx + b

Plug m  =  0.06, and (x, y)  =  (100, 14)

14  =  0.06(100) + b

14  =  6 + b

8  =  b

Step 4 :

Now, plug m = 0.06 and b = 8 in slope-intercept form equation of a line.

y  =  mx + b

y  =  0.06x + 8

step-by-step explanation: i dont