Lesson 9

Lesson 9.3F’08

Objectives: To solve a system of equations by

eliminat= ion.

= &nb= sp; To solve applications using a system of equations.

If one of coefficient= s of the variables is not one, then the elimination method might be better.

Solve the system by elimination.

&nb= sp; x + y =3D 9

&= nbsp; &nbs= p; 2x – y =3D 3

Solve the system by elimination.

x – 4y =3D= 14

&= nbsp; &nbs= p; 3x + 4y =3D 10

To solve a system of two linear equations by elimination:

1. Write each equation in standard fo= rm (Ax + By =3D C)

2. Use the multiplication principle to clear fractions or

decimals<= /span>.

3. Multiply one or both equations by a number(s) so that

they hav= e a pair of terms that are additive inverses.

4. Add the equations.

5. Solve the equation from step 4 for= the value of that

va= riable.

6. Using an equation containing both variables, substitute the

value yo= u found in step 5 for the corresponding variable and

solve for the value of the other variable.

7. Check the solution in the original equations.

Solve the system by elimination.

1. x + 4y =3D 0

5x – 3y =3D -23

2. 2x + 5y =3D 4

5x –= 7y =3D -29

4. 2x - y =3D 5

2x - y =3D 12

5. 4x - 2y =3D 5

12x - 6y = =3D 15

Set up a system of equations and Use it to solve each problem.

1. During the Olympics, Germany won twice as many gold

medals as Canada. If the total gold medals awarded t= o

both countries was 18, find the number of gold medals

awarded to each.

CW Worksheet 9.3

Homework Math XL section 9.3

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