SOLUTION: how do you work out -5x+3=6 x-y=4 by elimination

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: how do you work out -5x+3=6 x-y=4 by elimination       Log On


   

Question 822051: how do you work out -5x+3=6 x-y=4 by elimination
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
PUT EACH EQUATION INTO THE SAME FORM, PREFERABLY STANDARD FORM.
-5x%2B3=6 and x-y=4,
Assuming you meant:
-5x%2B3y=6 and x-y=4;
these are in the form, ax%2Bby=c.

MULTIPLY ONE OR BOTH EQUATIONS SO THAT THE COEFFICIENT ON ONE OF THE VARIABLES IS THE SAME FOR BOTH EQUATIONS.
-5x%2B3y=6 and 3%28x-y%29=3%2A4, 3x-3y=12 for the second equation.

SUBTRACT (OR ADD) ONE EQUATION FROM THE OTHER.
%28-5x%2B3y%29%2B%283x-3y%29=6%2B12
-5x%2B3y%2B3x-3y=18
-5x%2B3x=18
-2x=18

SOLVE FOR THE UN-ELIMINATED VARIABLE FIRST, AND THEN USE EITHER EQUATION TO FIND THE OTHER VARIABLE.
-2x%2F%28-2%29=18%2F%28-2%29
x=-9-----------part of the answer
'
x-y=4
-y=4-x
y=x-4
y=-9-4
y=-13------------------other part of answer