Find gradient f at the given point.

f(x,y,z)= ( (x^2+y^2+z^2)^(-1/2) ) + ln(xyz) , (-1,2,-2)

df/dx = -x/(x^2+y^2+z^2)^(3/2)

df/dy = -y/(x^2+y^2+z^2)^(3/2)

df/dz = -z/(x^2+y^2+z^2)^(3/2)

ok so after finding the partials with respect to x,y,z and plugging in the point I get the answer

-1/27 i - 2/27 j + 2/27 k

the books answer is

-26/27 i +23/54 j -23/54 k

Can anyone verify which answer is correct?