9x+3y=0

9x+3y=0   (1)

-36x-12y=0 (2)  this is the same as 9x+3y=0   (2b)     I divided both sides by -4

 

Now I can see that equation (2b) is the same as equation (1)

this means that there is an infinite number of solutions because they are exactly the same equation.

If you graphed them - they are the same line. 

Chris has ALSO answered this here. 

 

http://web2.0calc.com/questions/not-answer