Agenda for Thursday 11/29/12

• Questions on solving by graphing• Target Practice: PASS BACK• Lesson on Solving Linear Systems by

Substitution• Assignment…

Target 7a: I can solve linear systems by graphing, substitution, and elimination.

Solving Linear Systems by Substitution

y = 3x + 2

x + 2y = 11x + 2(3x + 2) = 11 x + 6x + 4 = 11 7x + 4 = 11 -4 -4 7x = 7 7 7 x = 1

Plug 3x + 2 in for y.Solve for x.

Plug 1 in for x.Solve for y.

y = 3(1) + 2y = 5

The solution is (1,5).

Lets try another one together!

x = 2y – 5

2x – y = 112(2y – 5) – y = 11 4y – 10 – y = 11 3y – 10 = 11 +10 +10 3y = 21 3 3 y = 7

Plug 2y – 5 in for x.Solve for y.

x = 2(7) – 5x = 9

The solution is (9,7)

Plug 7 in for y.Solve for x.

Try these…

y – 3x = 5

x = y – 5

y = 3x – 12

2y – 3x = 36

y – 3(y – 5) = 5y – 3y + 15 = 5 -2y + 15 = 5 -15 -15 -2y = -10 -2 -2 y = 5

x = 5 – 5 x = 0

The solution is (0,5)

2(3x – 12) – 3x = 36 6x – 24 – 3x = 36 3x – 24 = 36 +24 +24 3x = 60

3 3 x = 20

y = 3(20) – 12 y = 48

The solution is (20,48)

A Word Problem

Laura has $4.50 in dimes and quarters. She has 3 more dimes than quarters. How many of each type of coin does she have?

Step 1: Write a system of equations.

.10d + .25q = 4.50

d = q + 3

Step 2: Plug q + 3 in for d.

.10(q + 3) + .25q = 4.50 .1q + .3 + .25q = 4.50 .35q + .3 = 4.50 -.3 -.3 .35q = 4.2 .35 .35 q = 12

Step 3: Plug 12 in for q.

d = 12 + 3d = 15

12 quarters15 dimes

Agenda for Wednesday 11/28/12

• Assignment…– Lesson 7.2a Worksheet

Target 7a: I can solve linear systems by graphing, substitution, and elimination.