1. Solving By Substitution

5. Warm-Up!! Please pick up your calculator when you walk in!!
Use basic substitution to solve:
Y = 3x + 1 when x = 3
2y = x +4 when x = 6
8x + 14 = 2y + 2 when y = 2
Y + 8 = 2x + 10 when y = 4

6. Substitution Definition
Substitution means to replace a variable (letter) with a number that makes the equation or equations true.

7. Basic Substitution
Example: If a = 5, Find the value of y = 4a – 13

8. Solve by Substitution
Not only does substitution mean to replace a variable with a number; you can replace an equation too!

9. Steps to Solving Systems of Equations by Substitution
Step 1 – Solve an equation for one variable
Step 2 – Substitute
Step 3 – Solve the equation
Step 4 – Plug back in, to other the other variable
Step 5 – Check your solution

10. Example 1) Solve for x and y.
x + y = 5 y = 3 + x

11. Example 2) Solve for x and y.
3x – y = 4 x = 4y – 17

12. Example 3)
3y + x = 7 4x – 2y = 0

13. Example 4)
y = 2x – 4 y = 4x + 8

14. You Try! a) 2x + 4y = 4 b) x = 3 – y c) y = 4x
3x + 2y = x + y = x + y = -21