First you want to find m (which is slope). We use point slope formula to find this. Since we have two points we can do this.
[tex] y_{1}-y =m( x_{1}-x)[/tex]
0+4 = m(4-0)
Divide both sides by 4
m=1
Now we use point slope formula. We only need one point, it doesn't matter which, so take your pick (either 4,0 or 0,-4)
y=mx+b
0=1(4)+b
Simplify and solve for b
b=-4
Now you have your slope and y-intercept. That's all you need! :)
y=x-4 if your equation of the line