7.2: Elimination

Today we learned how to solve systems of equations by elimination. If done correctly, solving a problem by elimination should get you the same answer and solving problem by substitution. 

Steps to elimination:

1) obtain coefficients that differ only in sign

2) add equations to eliminate a variable

3) back substitution to solve for second equation

4) check your solution. 

Example problem: 

Solve this system of equations. 

5x+3y=9

2x+4y=14

Example solution by elimination. 

Note: in more complex problems where the coefficients in the original problem do not already differ only in sign, you will have to multiply both to get it to this form. 

Quick example: 

(5x-6y=9) (-2)

(2x-5y=10) (5)

Example solution by substitution. 

Math joke of the day

Q: Why did I divide sin by tan? 

A: Just cos.

source: http://www.jokes4us.com/miscellaneousjokes/mathjokes/