Is $f(x,y)=\frac{xy^3}{x^2+y^6}$ differentiable at $(0,0)$?
60498
Prove that $\lim_{(x,y)\rightarrow(0,0)} \frac{|x|^{a}|y|^{b}}{|x|^{c} + |y|^{d}}$ does not exist
106013
Given $f(x) = x + |x|$ for what values of $x$ is $f$ differentiable
60878
How to prove that $\lim_{(x,y) \to (0,0)} \frac{x^3y}{x^4+y^2} = 0?$
115635
Differentiability of antiderivative and continuity of derivative
16375
Is the function differentiable at $0$?
17475
Find the derivative of $y= \frac{(4x^3 +8)^{\frac{1}{3}}}{(x+2)^5}$
1641
Proving $f' = - \frac{\partial{F}/\partial{x}}{\partial{F}/\partial{y}}$
9211
$\int\frac{dx}{x-3y}$ when $y(x-y)^2=x$?
9270
Differentiable function, with $f'(x)=[f(x)]^2$
130322
Show that $f(x) = 0$ if $x = 0$ $f(x) = \text{exp}(-1/x^{2})$ if $x \neq 0$ is infinitely differentiable but not analytic at $x_{0} = 0$ `
25482
If a function is continuous and differentiable everywhere is the derivative continuous?
66560
Is a differentiable function always continuous?
131357
Prove that $f(x,y)=xy$ is differentiable using the definition
134122
When is differentiating an equation valid?
152877
Is a monotone differentiable function continuously differentiable?
62606
Non-existence of $\lim \limits_{(x, y) \to (0,0)} \frac{x^3 + y^3}{x - y} $
122003
From the limit definition of differentiability, determine where the function $f(x) = \sqrt{x}$ is differentiable?