SOLUTION: hi, two linear equations: x=-3y x+y=4 Which points represent the common solution for the two equations? the answer is (6, -2) how did they get that? thanks

Algebra ->  Linear-equations -> SOLUTION: hi, two linear equations: x=-3y x+y=4 Which points represent the common solution for the two equations? the answer is (6, -2) how did they get that? thanks      Log On


   

Question 75089: hi,
two linear equations:
x=-3y
x+y=4
Which points represent the common solution for the two equations?
the answer is (6, -2) how did they get that?
thanks
Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
TWO WAYS TO SOLVE THIS ALGEBRACIALLY:
X=-3Y NOW REPLACE X WITH (-3Y) IN THE OTHER EQUATION AND SOLVE FOR Y
(-3Y)+Y=4
-2Y=4
T=4/-2
Y=-2 ANSWER.
NOW SUBSTITUTE -2 FOR Y & SOLVE FOR X
X=-3(-2)
X=6 ANSWER.
--------------------------------------------------------
ANOTHER SOLUTION IS TO GRAPH THE TWO EQUATIONS. THUS:
X=-3Y
-3Y=X, Y=-X/3
X+Y=4, Y=-X+4
+graph%28+300%2C+200%2C+-6%2C+10%2C+-6%2C+5%2C+y+=+-x%2F3%2C+y+=+-x+%2B4%29+ (graph 300x200pixels, x from -6 to 10, y from -6 to 5, of TWO functions y = -x/3 and y = -x +4).