14.4 Differentiablity

How can we find if a function is differentialbe

• The function f is differentiable at (a,b) if f can be expressid in the form

  • $f(x,y)=f(a,b)+{\partial }_{x}f(a,b)\Delta x+{\partial }_{y}f(a,b)\Delta y+{ϵ}_1\Delta x$