Algebra
# Power Mean Inequalities

$\dfrac{a}{b} + \dfrac{b}{c} + \dfrac{c}{d} + \dfrac{d}{a}$

If $a, b, c$ and $d$ are any four positive real numbers, then find the minimum value of the expression above.

For $a,b,c>0$ and $a+b+c=6$. Find the minimum value of

$\large \left (a+\frac{1}{b} \right )^{2}+ \left (b+\frac{1}{c} \right )^{2}+\left (c+\frac{1}{a} \right )^{2}$

Let $x,y$ be positive reals such that $x+y =2$, find the maximum value of $x^{3}y^{3}(x^{3}+y^{3})$.