1. Equations as Relations Lesson for Glencoe Algebra I Math
By: Cathy Miller
Bartlett High School
Lesson for Glencoe Algebra I Math
Section 4-4
Algebra I Glencoe Mathematics 2004
The McGraw Hill Companies Inc.

2. Ways to write a relation
Set of ordered pairs
Table
Mapping
Graph
Equation in two variables

3. New Vocabulary
Equation in Two Variables – Equations with 2 different variables.
Solution to Equation in Two Variables – any point that makes a true statement when you substitute the x and y values into the equation.

4. Solve Using a Replacement Set
Replacement set = a set of possible
solutions.
Substitute the points to find the true solutions… these are the ones that make the equation true.
Solution set = the set of true solutions.

5. Solve -3x+y=7 if the replacement set is {(-5,0),(-3,-2),(2,13),(4,19)}
-3(-5)+(0)=7
15 = 7
-3(-3)+(-2)=7
7=7

6. Solve -3x+y=7 if the replacement set is {(-5,0),(-3,-2),(2,13),(4,19)}
-3(2)+(13)=7
7=7
-3(4)+(19)=7
7=7

7. Solve y=7+3x if the replacement set is {(-5,0),(-3,-2),(2,13),(4,19)}
Solution set = {(-3,-2),(2,13),(4,19)}

8. Solve Using a Given Domain
Domain = the x’s for your solution setlthat you can use
Substitute the x’s to find their y’s.
Solution set = the set (x,y)’s

9. Solve 9x+3y=15 if the domain is { 0,1,2,3}
First…solve the equation for y

10. Solve 9x+3y=15 if the domain is { 0,1,2,3}
y=-3x+5 y
y=-3(0)+5
= 5 1
y=-3(1)+5
= 2

11. x y y=-3x+5 y=-3(0)+5 = 5 1 y=-3(1)+5 = 2 2 y=-3(2)+5 = -1 3 y=-3(3)+5
Solve 9x+3y=15 if D={ 0,1,2,3} x y
y=-3x+5
y=-3(0)+5
= 5 1
y=-3(1)+5
= 2 2
y=-3(2)+5
= -1 3
y=-3(3)+5
= -4
Sol. Set={(0,5),(1,2),(2,-1),(3,-4)|