Question

How many solutions does the system 9x+y=3 9x-y=7 have?

Answer 1

These are two linear equations so they can have zero, one, or infinitely many solutions...

Subtracting one from the other eliminates x...

9x+y-9x+y=3-7

2y=-4

y=-2, making 9x+y=3 become:

9x-2=3

9x=5

x=5/9

So the single solution to this system of equations is the point (5/9, -2)