D is a notation for differential. There is a d2 in your formula because in the numerator there are two differentials. The formula is thus the second derivative of a function with respect to two variables.
I assume has counterclockwise orientation when viewed from above.
By Stokes' theorem,
so we first compute the curl:
Then parameterize by
where the -component is obtained from
with and .
Take the normal vector to to be
Then the line integral is equal in value to the surface integral,
Slope intercept form is y=mx+b
Y= y intercept
M = slope
B = x intercept
-2x-11y= 5 get the y by itself
-11y = 2x + 5 divide by -11
y = -2/11x + 5/11
slope is -2/11