1. 7.3 Elimination Method Using Addition and Subtraction

2. Elimination Method The third method used to solve systems of equations.

3. Elimination Method Example: Solve Soln: (4, -1) x - 3y = 7 3x + 3y = 9 (+) 4x = 16 x - 3y = 7 x = 4 (4)- 3y = 7 - 3y = 3 y = -1

4. Elimination Method Example: Solve Soln: (1, -3) 2x - 3y = 11 5x - 3y = 14 (-) x = 1 2x - 3y = 11 -3x = -3 2(1)- 3y = 11 2 - 3y = 11 - 3y = 9 y = -3

5. Elimination The sum of two numbers is 48, and their difference is 24. What are the numbers? x + y = 48 x – y = 24 (+) 2x = 72 (36) + y = 48 Soln: (36, 12) x = 36 y = 12

6. Elimination Three times one number added to another number is 18. Twice the first number minus the other number is 12. Find the numbers. 3x + y = 18 2x – y = 12 (+) 5x = 30 3(6) + y = 18 Soln: (6, 0) x = 6 18 + y = 18 y = 0

7. CAUTION!! BEFORE YOU BEGIN, equations must be lined up! (x’s on top of x’s, y’s on top of y’s, #’s on top of #’s and = sign on top of = sign.

8. Homework: Pg p385: 13-33odd