Find the Line Tangent to the Surface Given by the Function

Essay

Find the line tangent to the surface given by the function at the specified point $P$ in the direction of the vector $\vec { u }$ $f ( x , y ) = x ^ { 2 } + x y , P = ( 1,2 ) , \vec { u } = \left\langle \frac { 1 } { 2 } , \frac { \sqrt { 3 } } { 2 } \right\rangle$