What is the value of $\sqrt{729} + \sqrt{72.9} + \sqrt{7.29}$?

Find the value of the following expression up to four places of decimals:
$\left[1+\frac{1}{1 \times 2}+\frac{1}{1 \times 2 \times 4}+\frac{1}{1 \times 2 \times 4 \times 8}+\frac{1}{1 \times 2 \times 4 \times 8 \times 16}\right]$

$1 . \overline{27}$ in the form $\frac{p}{q}$ is equal to

Which of the following is true?
$I.$ $\frac{1}{\sqrt[3]{12}} > \frac{1}{\sqrt[4]{29}} > \frac{1}{\sqrt{5}}$
$II.$ $\frac{1}{\sqrt[4]{29}} > \frac{1}{\sqrt[3]{12}} > \frac{1}{\sqrt{5}}$
$III.$ $\frac{1}{\sqrt{5}} > \frac{1}{\sqrt[3]{12}} > \frac{1}{\sqrt[4]{29}}$
$IV.$ $\frac{1}{\sqrt{5}} > \frac{1}{\sqrt[4]{29}} > \frac{1}{\sqrt[3]{12}}$

The value of $\frac{1}{a^{2}+a x+x^{2}}-\frac{1}{a^{2}-a x+x^{2}}+\frac{2 a x}{a^{4}+a^{2} x^{2}+x^{4}}$ is

$3 \div \left[ (8 - 5) \div \left\{ (4 - 2) \div \left( 2 + \frac{8}{13} \right) \right\} \right] = ?$