Section+7.3+-+Solving+Systems+with+Addition+or+Subtraction

Elimination with Adding & Subtracting

Methods: 1) Graphing 2) Substitution 3) Elimination -Combine the two equations to eliminate/cancel a variable.
 * you want the coefficients of 1 of the variables to be opposites.**

ex. Solve: ex. Solve: 2x+5y=11 4x-5y=7 __6x=18__ 6 6 x=3 (now plug 3 in for x) 6+5y=11 -6 -6 __5y__=__5__ 5 5 y=1 (write as ordered pair) (3,1)

ex. Solve: 5x-7y=-26 11x-7y=10(divide them all by negative 1 to make 7y opposites) -11x+7y=-10 __-6x=-36__ -6 -6 x=6 30-7y= -26 -30 -30 __-7y= -56__ -7 -7 y=8 (6,8) --> REMEMBER : ORDERED PAIRS.

ex. Solve: 4a+b=5 -6a-b=-6 __-2a= -1__ -2 -2 a=1/2 (now plug 1/2 in for a) 2-b=5 -2 -2 b=3 (1/2,3)