1. Warm Up #3 1. Evaluate 5x + 2y for x = 2 and y = –4. 2 ANSWER
2. Find the x and y intercepts of the equation
–3x + 4y = 12.
ANSWER
(-4 , 0) (0 , 3)

4. Recall Graphing from Standard Form
Graph both lines on the same graph: 3x – 2y = and 5x + 2y = 10
Line 1:
x int. ( , 0 ) 2
y int. ( 0 , ) -3
Line 2:
x int. ( , 0 ) 2
y int. ( 0 , ) 5
Recall Graphing from Standard Form

5. Solve a system graphically
EXAMPLE 1
Solve a system graphically
Graph the linear system and estimate the solution. Then check the solution algebraically.
4x + y = 8
Equation 1
(2 , 0) (0 , 8)
2x – 3y = 18
Equation 2
(9 , 0) (0 , -6)
SOLUTION
Begin by graphing both equations, as shown at the right. From the graph, the lines appear to intersect at (3, –4). You can check this algebraically as follows.

6. Solve a system graphically
EXAMPLE 1
Solve a system graphically
Equation 1
Equation 2
4x + y = 8
2x – 3y = 18
4(3) + (–4) 8 = ? = ?
2(3) – 3( – 4) 18 = ?
12 –4 8 = ?
8 = 8
18 = 18
The solution is (3, –4).

7. GET THE WHITEBOARDS 

8. Graph both lines on the same graph: y = -2x + 4 and y = 3x - 2
They Intersect
Estimate
( 1.2 , 1.8 )

9. Check (1.2 , 1.8)
y = -2x and y = 3x - 2
1.8 = -2(1.2) and = 3(1.2) - 2
1.8 = and =
1.8 = and = 1.6
Not exact, but close. Many times when estimating from a graph you can only get an approximation.

10. Graph both lines on the same graph: 3x – 2y = 6 and 5x + 2y = 10
x int. ( , 0 ) 2
y int. ( 0 , ) -3
Line 2:
x int. ( , 0 ) 2
y int. ( 0 , ) 5
They intersect at the point ( 2 , 0 )

11. Graph this system of linear equations, then
Give the solution:
y = 1/5 x + 2
y = -5/3 x + 5

12. Graph this system of linear equations, then
Give the solution :
y = 2x - 1
y = 2x + 2

13. Graph this system of linear equations, then Give the solution :
y = 1/3 x + 2
-x + 3y = 6
Add x and divide by 3
y = 1/3 x + 2

14. Classwork Assignment
WS 3.1 (1-11 odd and 17-20)