. You forgot the f(x)
The surface area is given by
This simplifies down to
Now, can you integrate that. A little easier now?.
What I think I need help with is (forgive my Latex ignorance):
. . ._____
∫ √1+1/x dx
I have no idea how to integrate this.
In case I set up the integral wrong, the original question calls for evaluating the surface area of y=2√x rotated around the x-axis (on the interval from 4 to 9).
So first derivative (1/√x)
First derivative squared (1/x)
Into the form of (arc length x 2π):
. . . . ._____
2π ∫ √1+1/x dx (evaluated on aforementioned interval.)