Shooting an arrow in the direction of the gradien

[chaotixmonjuish]

If you are given a point (1,2,9), and a gradient <2,1,2>. How can you tell that if you show an arrow, it would hit the point (5,4,13). The arrow is being shot in the direction of the gradient.

where f(x,y,z)= x^2+y^2/4+z^2/9

 

[HallsofIvy]

If you are given a point (1,2,9), and a gradient <2,1,2>. How can you tell that if you show an arrow, it would hit the point (5,4,13). The arrow is being shot in the direction of the gradient.

where f(x,y,z)= x^2+y^2/4+z^2/9

What does f have to do with the motion of the arrow?

 

[chaotixmonjuish]

I just included that to show how I calculated the gradient.