1. Bell Ringer Solve for x. 2x – 5 = 35 – 18x

2. Today’s LEQ: How do you solve a system of equations by substitution? We already know we can solve a system of equations by graphing… What might make graphing to solve a system difficult? Not a nice y-intercept, the lines may not intersect at a definite (x,y)

3. Solving Systems of Equations by Substitution – Part 1 Steps 1.)_____________ an equation for either x or y. 2.)________________________ your expression into the _______________ equation to find the value of x or y. 3.)________________________ your value to find the ______________ missing value of x or y. Solve Substitute other Substitute other

4. Example y = -x + 10 y = 2x + 1 Steps 1.)Solve an equation for either x or y. 2.) Substitute your expression into the other equation to find the value of x or y. 3.) Plug in your value to find the other missing value of x or y.

5. Let’s do some more…. Find the solution to the system of equations by using substitution: 1. y = 3x + 5 y = -x + 13

6. Let’s do some more…. Find the solution to the system of equations by using substitution: 2. x = -y + 10 x = 2y + 1

7. Let’s do some more…. Find the solution to the system of equations by using substitution: 3. y = 2x y = 5x – 33

8. Let’s do some more…. Find the solution to the system of equations by using substitution: 4. -3y = x x = -y + 14

9. Quick Check Solve the system. 2 + 3y = x x = -2y - 8

10. Now.…. Help me solve the following equation for y. 2x – 8y = 24

11. Solving Systems of Equations by Substitution – Part 2 Steps 1.)_____________ an equation for either x or y. 2.)________________________ your expression into the _______________ equation to find the value of x or y. 3.)________________________ your value to find the ______________ missing value of x or y. Solve Substitute other Plug in other

12. Example y = 2x – 2 3x + 2y = 38 Steps 1.)Solve an equation for either x or y. 2.) Substitute your expression into the other equation to find the value of x or y. 3.) Plug in your value to find the other missing value of x or y.

13. Let’s do some more…. Find the solution to the system of equations by using substitution: 1. y = -4x 12x + y = 48

14. Let’s do some more…. Find the solution to the system of equations by using substitution: 2. 2x = 4y x = 30 – 13y

15. Let’s do some more…. Find the solution to the system of equations by using substitution: 3. x + y = 1 15 – 8y = x

16. Let’s do some more…. Find the solution to the system of equations by using substitution: 4. 6x = 2y y = 4x – 4

17. Paper Quick Check (Graded?)