SOLUTION: solve by addition or substitution. 20x-5y=-12 and y = 4x+3. If anyone can help, I would be so grateful.

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: solve by addition or substitution. 20x-5y=-12 and y = 4x+3. If anyone can help, I would be so grateful.      Log On


   

Question 91455: solve by addition or substitution. 20x-5y=-12 and y = 4x+3. If anyone can help, I would be so grateful.
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
20X-5Y=-12
Y=4X+3 OR 4X-Y=-3 NOW MULTIPLY THIS EQUATION BY -5 & ADD.
-20X+5Y=15
20X-5Y=-12
----------------
0+0=3 NO UNIQUE SOLUTION FOR X&Y.
PROOF
20X-5Y=-12 OR -5Y=-20X-12 OR Y=-20X/-5-12/-5 OR Y=4X+12/5 (RED LINE)
Y=4X+3 (GREEN LINE)
+graph%28+300%2C+200%2C+-6%2C+5%2C+-10%2C+10%2C+y+=+4x+%2B12%2F5%2C+y+=+4x+%2B3%29+ (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions y = 4x +12/5 and y = 4x +3).