8.3 Solving Systems of Equations by ELIMINATION (addition) ESSENTIAL QUESTION: How can you solve a system of equations by adding?

When we solve a System of Equation using the elimination method, we ELIMINATE (get rid of) one variable by ADDING OPPOSITES and solving for the other variable.

When using the ELIMINATION method, look for like VARIABLES that have OPPOSITE COEFFICIENTS. ADD all like terms (vertically). The opposite terms are eliminated. (Remember: a number plus its opposite = 0) To find the value of the eliminated variable, plug the known value into EITHER equation (use the simplest of the two equations) Solve for the remaining variable using algebra 1-step or 2-step rules. STACK the like terms so they line up vertically. (Sometimes this is already done) WHAT TO DO

Example: Solve this system of equations using elimination You’re HALFWAY done! Add like terms vertically PPOSITES Notice “Like terms” are lined up vertically

Example: Solve this system of equations using elimination You’re HALFWAY done! PPOSITES

Solve this system of equations using elimination You’re HALFWAY done! PPOSITES YOUR TURN DON’T FORGET TO CHECK YOUR ANSWER – PLUG THE VALUES IN TO BOTH EQUATIONS