1. Plickers!!! Remember your # No writing/tearing/bending
Always return where they belong
Let’s have fun with this!

2. Bellwork (1 of 3)
Which of the following items was owned by the fewest U.S. homes in 1990? A. home computer B. CD player C. cordless phone D. dishwasher

3. Q #2
What is the slope of y=2x+5? 5
5/2
2/5 2

4. Q #3
What is the y-intercept of y=2/3x-6? -6
2/3 6
3/2

5. Solving Systems of Equations by Graphing
Goals: ~Solve systems of equations by graphing
~Determine whether a system has 1, infinitely many, or no solutions

6. Key Term
System of Equations: Two or more equations with the same variables

7. 3 Possibilities… One solution No Solution Infinitely many solutions
same line for both eqns

8. Steps to solve by graphing
Put equations in slope-intercept form
Graph: Plot the y-intercept then follow the slope ( ) to get the next point
The intersection point is the solution
Note: You can check by plugging your answer in

9. Basically…
Get in y=mx+b form
Graph
Find intersection

10. Example 1: Solve by graphing.
Y= -x+3
Y= 3/2x-2
Answer: 1. Both are already in
slope-intercept form
2. Graph. Remember: y-int first then use
slope to get next point
3. Find the intersection point. This is
your solution.

11. Graph
Solution is
(2,1)

12. TRY IT! Solve by graphing…
Y=x+2
Y=3x-2

13. Solution:
(2,4)

14. Example 2: Solve by graphing
2x+y = 5
x – y = 1
Answer: Write each equation in slope-intercept form.
2x+y=5 -->
y=-2x+5
x- y = 1 -->
-y=-x+1 --> y=x-1
Graph. (Graph y-int then follow the slope[rise/run] to get the next point)
The point where they cross is the solution

15. Graph
(2,1) is the
solution.

16. Answer:
They cross only once so the solution is (2,1)

17. TRY IT! Solve by graphing…
2x-y= -5
-2x-y= -1

18. Answer:
(-1,3)

19. Infinitely many solutions:
How to know how many answers there are just by looking at the system of linear equations
One Solution:
Different slope
Infinitely many solutions:
Same equations (same slopes and y-intercepts)
No Solution (parallel):
Same slope & different y-intercept

20. y = -x + 3 2y = -2x + 6 Solution : y = -x + 3
Example 3: Without graphing, write whether there will be one solution, infinitely many solutions, or no solutions
y = -x + 3
2y = -2x + 6
Solution :
Put in slope-intercept form
Look at the slope and y-intercept to get solution.
y = -x + 3

21. Answer
They both make the same graph, so there are infinitely many solutions!! 

22. TRY IT! Without graphing, write whether there will be one solution, infinitely many solutions, or no solutions
2a. y = 3x + 2
y = 3x -5
2b y = ½ x -6
y = 4x + 10

23. Mr. Monroe bought 2 lbs of cheddar cheese and 3 lbs of turkey
Mr. Monroe bought 2 lbs of cheddar cheese and 3 lbs of turkey. He paid $ Ms. Stewart paid $18.35 for 1.5 lbs of cheese and 2 lbs of turkey. Write the system of equations.
Let’s look at each person separately…
Mr. Monroe:
2x+3y=26.35
Ms. Stewart
1.5x+2y=18.35
How would I start to try and solve
this by graphing?