slope of line

Question

Use the two points whose coordinates are indicated on the graph to find the point-slope equation of the line that models the number of screens, y, in thousands, x years after 1995.

 

 

the two points are (1,26) and (5,42)

Answer 1

Since this is a modeling problem, It would help to know what the points represent. I'm going to assume the axis give a slope in thousands of screens per year.

 

Point-slope equation of a line:

y − y₁ = m(x − x₁)

 

First find the slope, m using the points (1,26) and (5,42)

 

m = (y − y₁)/(x − x₁)

 

m = (42-26)/(5-1)

 

m = (16)/(4) = 4

 

Add the slope, m to the equation.

 

y − y₁ = 4(x − x₁)

 

Since we want x in years after 1995. Use the point: x =0 yrs and y = the number of screens sold in 1995 for (x₁, y₁)

 

y - ? = 4(x - 0)