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Warm Up Graph the lines on the same grid and identify the point where they meet. 1. y=2x-2 2. y=x+1

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Objective You will be able to: solve systems of equations by graphing.

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What is a system of equations? A system of equations is when you have two or more equations using the same variables. The solution to the system is the point that satisfies ALL of the equations. This point will be an ordered pair (x,y). When graphing, you will encounter three possibilities.

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Intersecting Lines The point where the lines intersect is your solution. The solution of this graph is (1, 2) (1,2)

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Parallel Lines These lines never intersect! Since the lines never cross, there is NO SOLUTION! Parallel lines have the same slope with different y-intercepts.

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Coinciding Lines These lines are the same! Since the lines are on top of each other, there are INFINITELY MANY SOLUTIONS! Coinciding lines have the same slope and y-intercepts.

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What is the solution of the system graphed below? 1. (2, -2) 2. (-2, 2) 3. No solution 4. Infinitely many solutions

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Example 1: Solve this system y= -x +7 y= x -1 All we need to do is graph the two lines and see where they intersect.

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Example 1 Cont… Start by plotting a point at the y intercept. Then count up/down and to the right for the slope. Do the same thing for the second equation. Check to see where the lines cross. That point is your answer. Always (x,y). X is first!!! y= -x +7 y= x -1

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Example 1 Cont… The last step is to check your answer. You do this by plugging the solution point (x,y) into each equation and checking to see if it works.

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Example 1 cont… Our equations are: y= -x +7 y= x -1 And our solution is (4,3) So: 3 = - 4 +7 And 3 = 4-1 It works! So we know we did it right and (4,3) is in fact our solution!

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Example 2: You try! y= 4x – 1 y= -x +4

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Example 2 cont… Solution: (1,3)

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Solving a system of equations by graphing. Let's summarize! There are 3 steps to solving a system using a graph. Step 1: Graph both equations. Step 2: Do the graphs intersect? Step 3: Check your solution. Graph using slope and y – intercept or x- and y-intercepts. Be sure to use a ruler and graph paper! This is the solution! LABEL the solution! Substitute the x and y values into both equations to verify the point is a solution to both equations.

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Homework http://www.kutasoftware.com/FreeWorks heets/Alg1Worksheets/Systems%20of% 20Equations%20Graphing.pdf http://www.kutasoftware.com/FreeWorks heets/Alg1Worksheets/Systems%20of% 20Equations%20Graphing.pdf Problems 1-4

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