Symbol
Problem
$f:R^{2}→R,f\left(x,y\right)$ $=4x^{2}+y^{2}$ then the value of the directional derivative of $f$ at the point $\left(1,1\right)$ in the direction of $\left(1,2\right)$ is $\left(A\right)$ $\left(B\right)$ $\dfrac {12} {\sqrt{15} }$ $\dfrac {8} {\sqrt{5} }$ $\dfrac {18} {\sqrt{5} }$ $\left(0$ (C) $\right)$ $D\right)$ $\dfrac {12} {\sqrt{5} }$
Algebra
Search count: 107
Solution