i know that the maximal growth is the gradiend of a function.

the formula is:

so when i am given a function

i am was told that it growth on point M(1,2,6) in direction is 1

what is the gradient of f (maximal growth).

i tried to get it like this:

first of all i need a function which looks like this f(x,y,z)=...

in order to find the gradient

i dont know how to do the gradient of a function which i was given.

if i substiute the point

f(1,2,6)=3-10=7

i know i should write

????