SOLUTION: Solve the following system using the substitution method: x=-3y+4 and 3x+9y=12. I know how to solve the equation using the substitution method, but I don't know how to get my answ

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: Solve the following system using the substitution method: x=-3y+4 and 3x+9y=12. I know how to solve the equation using the substitution method, but I don't know how to get my answ      Log On


   

Question 675181: Solve the following system using the substitution method: x=-3y+4 and 3x+9y=12. I know how to solve the equation using the substitution method, but I don't know how to get my answer correct with the y variable.
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

+x=-3y%2B4 ...........1...substitute in 2
3x%2B9y=12.............2
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3%28-3y%2B4%29%2B9y=12.............2...solve for y
-9y%2B12%2B9y=12

-9y%2B9y=12-12
0=0..............there are an infinite number of solutions and the system is dependent
so, the two lines are identical (one lies perfectly on+top+of+the+other) and intersect at all points of both lines