I need help with the slope please

m=2

Step-by-step explanation:

rise over run: rise=8 run=4 so it is m=8/4 or m=2

Show this is false:  For each non-zero integer x there exists integer y such that xy=1

Let's take x=2, so our equation is

2y = 1

That has solution y=1/2 which isn't an integer, not in Z*.  There's no integer y that can solve this equation.  We found an x where the y doesn't exist, that's a counterexample to the claim.