Point-Slope Form of a Line2.21

Domino Effect #4

http://www.mathalicious.com/lessons/domino-effect/teach

Finding the Linear Equation

The information we had about the pizzas did not tell us the price per topping for each pizza size or the base price for a pizza.

We were still able to find the equation of the line.

How?

From Pizza to Point-Slope Form of a Line

(16.95 – 13.97) = 1.49(4 – 2)

(y2 – y1) = m(x2 – x1)

(y – y1) = m(x – x1)

Point-Slope Form of a Line

Point-slope form

A linear equation written using the slope and one point from the line

(y – y1) = m(x – x1)

Steps

Determine the slope of the lineLabel the x and y values of one pointSubstitute these values in for m, x1, and

y1

Example

Write the equation for the line that has a slope of 5 and passes through the point (-1, 8).

Example

Write the equation for the line that passes through the points (-3, 0) and (1, -2).

Practice

Write the linear equation with the following set of characteristics.

1) Slope of -4; passes through (8, 5)

2) Slope of ½; passes through (6, -2)

3) Passes through (1, 4) and (7, 5)

4) Passes through (-1, 5) and (1, -3)

5) Passes through (-3, 0) and (-2, -5)

6) Passes through (-4, 3) and (2, 3)