Find the eaquation

Question

Dire subscribes to an internet service on her first bill she was charged $16.20 for 18 hours and on her second bill she was charged $17.75 for 23 hours of service? Find the eaquation and graph

Answer 1

In the following explanation, I'm assuming the equation we are trying to find is that of a line (the relationship is linear).

Let x1 = number hours for first bill

Let y1= charge for first bill

Let x2 = number hours for second bill

Let y2 = charge for second bill

We thus have two sets of coordinates (x1,y1) and (x2,y2)

where (x1,y1) = (18,16.20)

and (x2,y2) = (23,17.75_

Assuming a linear relationship, the equation would be of the form y=mx+b

m = (y2-y1)/(x2-x1) = (17.75-16.2)/(23-18) = 0.31

so y = 0.31x + b

Determine b, we substitute in one of the coordinate pairs for x,y, choosing (x1,y1) we get

16.2 = 0.31(18) + b

b = 10.62

So the final equation is y = 0.31x + 10.6