1. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Direct Variation
What is the length between each pair of vertical posts next to each other?
How are the base and the height of the large rectangle related?
8ft 4
= 2ft
height base
6 8 =
Algebra 2 Foundations, pg 74

2. Ch 2, L2
Students will be able to write and interpret direct variation equations.
3. Using the information from #2, create an equation to help determine the heights of each post.
4. Substitute the base values to determine each post height.
3 4
height =
base
Algebra 2 Foundations, pg 74

3. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Direct Variation
The post heights in the Solve It satisfy a relationship called direct variation.
Focus Question
When do you use direct variation?
Direct variation relates quantities where the ratio of corresponding values is constant.
Algebra 2 Foundations, pg 74

4. Ch 2, L2
Students will be able to write and interpret direct variation equations.
You can write a formula for a direct variation function as y = kx, or = k, where k ≠ 0. x represents input values, and y represents output values. The formula = k says that, except for (0, 0), the ratio for all output-input pairs equals the constant k, the constant of variation.
In a direct variation, is the same for all pairs of data where x ≠ 0. So, = is true for the ordered pairs (x1, y1) and (x2, y2), where neither x1 nor x2 is zero.
y x
y x
y x
y1 x1
y2 x2
Algebra 2 Foundations, pg 74

5. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Algebra 2 Foundations, pg 74

6. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Algebra 2 Foundations, pg 75

7. Ch 2, L2
Students will be able to write and interpret direct variation equations.

8. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Algebra 2 Foundations, pg 76

9. Ch 2, L2
Students will be able to write and interpret direct variation equations.

10. Ch 2, L2
Students will be able to write and interpret direct variation equations.
You can use the direct variation function y = kx to model some situations.
Algebra 2 Foundations, pg 76

11. Ch 2, L2
Students will be able to write and interpret direct variation equations.

12. Ch 2, L2
Students will be able to write and interpret direct variation equations.
The graph of a direct variation function is always a line through the origin.
Algebra 2 Foundations, pg 77

13. Ch 2, L2
Students will be able to write and interpret direct variation equations.
Write and graph a direct variation that passes through each point.
15. (6, 2) (-1, 5)