Answer :

Steps
1. Do the point slope form
Y-Y1=4(X-X1)
Y-4=4(x-2)
Y-4=4x + (-8)
2. Add 4 on both sides
Y= 4x-4
3. Your answer is
Y=4x-4
y=mx+b
4=4(2) + b
4=8 + b
4-8=8-8 +b
-4=b
y=4x -4