Let $z = f ( x , y )$ Such That $\nabla f ( - 1,2 ) = ( 3 , - 4 )$

Essay

Let $z = f ( x , y )$ such that $\nabla f ( - 1,2 ) = ( 3 , - 4 )$ . Find an equation of the tangent line to the level curve of $f ( x , y )$ that passes through point $( - 1,2 )$ .