It’s c
8 squared is 64
If you multiply that by 4 you will get 256 pi
You will not have to approximate it.
Gradient = change in y /change in x so -6-2 =-8 / -16-4 = -20 so -8/-20 = 0.4 so gradient = 0.4
The slope of that line is “undefined”. The slope of horizontal lines are 0 and the slope of vertical lines are undefined.