1. Thursday Warmup
Homework Check: Document Camera

2. SWBAT solve systems of equations by elimination.
Math 1B
Unit 0 Day 7
Objective:
SWBAT solve systems of equations by elimination.

3. Solving Systems Using Elimination
Obj: To solve systems by adding or subtracting.
Elimination Method: A method for solving a system of linear equations. You add or subtract the equations to eliminate a variable.

4. Ex 1: Solve by elimination. 2x + 3y = 11
Step 1: Eliminate x because the sum of the coefficients is 0.
2x + 3y = 11
–2x + 9y =1
0 + 12y = 12 Addition Property of Equality
y = 1 Solve for y.
Step 2: Solve for the eliminated variable x using either original equation.
2x + 3y = 11 Choose the first equation.
2x + 3(1) = 11 Substitute 1 for y.
2x + 3 = 11 Solve for x.
2x = 8
x = 4

5. Ex 1 (continued)
Since x = 4 and y = 1, the solution is (4, 1).
Check: See if (4, 1) makes true the equation not used in Step 2.
–2(4) + 9(1) Substitute 4 for x and 1 for y into the second equation. –
1 = 1

6. Ex 2: On a special day, tickets for a minor league baseball game were $5 for adults and $1 for students. The attendance that day was 1139, and $3067 was collected. Write and solve a system of equations to find the number of adults and the number of students that attended the game.
Define: Let a = number of adults
Let s = number of students
Relate: total number at the game total amount collected
Write: a s = a s = 3067
Solve by elimination.

7. Ex 2 (continued)
Step 1: Eliminate one variable.
a + s = 1139
5a + s = 3067
–4a = –1928 Subtraction Property of Equality
a = 482 Solve for a.
-( )
Step 2: Solve for the eliminated variable using either of the original equations.
a + s = 1139 Choose the first equation.
s = 1139 Substitute 482 for a.
s = 657 Solve for s.
There were 482 adults and 657 students at the game.
Check: Is the solution reasonable? The total number at the game was , or The money collected was $5(482), or $2410, plus $1(657), or $657, which is $3067. The solution is correct.

8. Activity:
Systems of Equations by Elimination to Notebook

9. Systems of Equations by elimination WS
Homework:
Systems of Equations by elimination WS