Section A: Elimination Method

1) Lesson Objectives:

You should be able to

• solve simultaneous equations by Elimination Method and Substitution Method.

• to check you answer using a calculator.

Always look through all examples in textbook before lesson.

Please watch the video lessons after this section.

Solve the following simultaneous equations:

x + 3y = 5

2x - 5y = -12

Steps:

1. Label both equations as (1) and (2)

2. Choose a variable that you would like to eliminate

3. Make sure the coefficient of the variable that you have chosen to eliminate is the same for both the equations

4. If it is not the same, multiply a constant to find the LCM for both

5. Add or subtract the equations to eliminate the variable chosen

If the variable have the same signs - Subtract the 2 equations

If the variable have different signs - Add the 2 equations

6. Once you find one variable, remember to substitute and find the other variable

7. You must have 2 values, one for each variable as your answer

8. Check if you answer is correct by using your calculator

Section B: Substitution Method

Please watch the video lessons after this section.

Solve the following simultaneous equations:

x + 3y = 5

2x - 5y = -12

Steps:

1. Label both equations as (1) and (2)

2. Choose a variable that have coefficient 1.

3. Make sure the variable is the subject of the equation

4. Substitute the new equation into the other equation

5. Once you find one variable, remember to substitute and find the other variable

6. You must have 2 values, one for each variable as your answer

7. Check if you answer is correct by using your calculator

Using Calculator to check answer for simultaneous equations

NOTE: If you calculator is Casio fx-96SG Plus, please follow the steps.

STEPS:

1. Press MODE SETUP

2. Press 3 for EQN

3. Press 1: anX +bnY=Cn

4. You will see a square bracket with row a, b and c with column by the side 1 and 2. There is 6 small rectangles in the bracket.

5. a and b represents your variables and c represents your constant.

6. Make sure the equation is of the format anX +bnY=Cn where

an represents coefficient of X,

bn represents coefficient of Y,

Cn represents your constant.

7. Key in the coefficient of each variable plus the constant with the correct sign.

8. When your finish keying in all 6 digits, press equal sign.

9. The first value will be the answer for variable x. Press equal again and the next value will be the answer for variable y.

Do note, the questions are not from your Express textbook so just look the equations and practice with the calculator.

2) Checking for Understanding / Reflections:

Answer the following using the Padlet Link.

Padlet Link:

2-5: https://padlet.com/Mrs_Loh/25_Math_Padlet1_2021

2-7: https://padlet.com/MrsValerieLoh/27_Math_Padlet1_2021