## Max rate of descent , gradient?

Can anyone help me with the following question?
Find the path of the steepest descent along the surface z=x^3 + 3y^2 from the point (1, -2, 13) to (0,0,0)
Note: the general solution of the differential equation f ' (t)-kf(t) =0 is
f(t) = ce^kt, where c is an arbitary number
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I understand that max rate of change occurs in the direction of the gradient, and max descent occurs in the -gradient(f) direction

But I don't know what to do with the 2 points..and how it has anything to do with the formula given as a hint..(probably, it has nothing to do with it)

Can anyone help me with this?
Thanks so much