Please solve 1, 2, 31.2.3. Let \( f(x, y)=x^{2}-x y+5 y^{2} \). Then \[ f_{x}(4,1)= \] and \( f_{y}(4,1)= \) What is the directional derivative of \( f(x, y) \) at \( (x, y)=(4,1) \) in the direction \( \left\langle\frac{3}{5}, 2 answers