Answer:
A system of equations has infinitely many solutions when the two lines representing the equations coincide. i.e. the two equations are the same or a multiple of each other.
2y - 4x = 6
2y = 4x + 6
2y = 2(2x + 3)
y = 2x + 3
-y = -(2x + 3)
-y = -2x - 3
Hence the other equation is -y = -2x - 3
Explanation: