Quiz 2



Name:__________________________________________ Date:______________________ Period:________

Section 8.5 Day 2

Determining the Equation of a Line

The 3 forms of an equation of a line are:

Slope-Intercept Form Point-Slope Form Standard Form

y = mx + b y – y1 = m(x – x1) Ax + By = C

m = slope m = slope slope = [pic]

b = y-intercept (x1, y1) given point y-intercept = [pic]

* use given slope and y-intercept * use given a point and slope *** NEVER start here

or given 2 points

To write the equation of line:

➢ Pick the form that matches the information you are given { [pic]or y–y1 = m(x–x1) }

➢ Substitute given information into the corresponding equation

➢ Solve equation for the appropriate form in the directions

➢ Given a graph:

o Find your y-intercept (b) and slope (m)

➢ Given two points:

o Find the slope

o Pick a point

o Use point-slope to write the equation of the line

➢ Given intercepts:

o Write the intercepts as ordered pairs

o Find the slope

o Substitute slope and y-intercept into [pic]

Write an equation of the line in slope-intercept form of each line described.

1. slope 2; y-intercept 15 2. slope [pic]; y-intercept [pic] 3. slope –3, (–1, 2)

Write an equation of the line in standard-form form of each line described.

4. slope [pic]; x-intercept –3 5. slope 0 , through (1, –4) 6. (4, –3) and (3, –6)

7. y-intercept = 3, 8. horizontal line 9. vertical line

x-intercept = – 4 through (–5, –12) through (9, –15)

Write an equation of the line in slope-intercept form of each line graphed.

10. 11. 12.

13. 14. 15.

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