It can be a function if it's horizontal because it's only touching each point once, it can't be a function for a vertical line because it's straight up and down and it'll hit every point
The are is the whole area minus the inner:
(z+4)(z+4)-(z)(z)
Expand:
z^2+8z+16-z^2
Simplify:
8z+16
Answer:
8z+16 OR 8(z+2)
-8 + k = -17
k = -17 + 8
k = 8 -17
k = -9
