derivatives.
f(x)=(1/-7x^12)
f'(2)=?
f'(-1)=?
d/dx (top/bottom) = (bottom d/x top - top d/dx bottom) / bottom^2
f(x) = (-1/7) x^-12
f'(x) = (-1/7) (-12) x^-13
f'(x) = (12/7) x^-13
alternatively
f(x) = (-1/7) (1/x^12)
f'(x) = (-1/7) (x^12 * 0 - 1*12*x^11)/x^24
= (-1/7) (-12 / x^13)
= 12/(7 x^13) which is (12/7) x^-13
Now
substitute 2 for x
and
substitute -1 for x