given a two points (x1,y1) and (x2, y2)

Question

the cost of a classified ad is based on a daily rate plus a flat surface feet when they cost $3.50 and 4 days cost $8.00 write and solve a linear equation to find the cost of a 7 day ad

 

 

 

i honestly don't know how to solve this

Answer 1

We have for (x1, y1) the following (1,$3.50), x-axis for days and y-axis for the cost in $. The (x2, y2) is (7, $8.00)

 

The slope M can be calculated for the two points: m=(y2-y1)/(x2-x1)

 

Then m=(8-3.5)/(7-1)=4.6/6=3/4

 

The general equation for a line is y = m x + b where m is the slope and b is the y-intercept.

 

For the first point (x1,y1) and having m, then we can get b

 

Then 3.5 = (3/4) (1) + b

 

Finally b = 3.5 - (3/4) = (14 - 3)/4  and b = 11/4

 

The final equation for the straight line is  y = (3/4) x + (11/4)