MaxWong

$\dfrac{rs}{t}+\dfrac{st}{r}+\dfrac{tr}{s}\\ =\dfrac{r^2s^2}{rst}+\dfrac{s^2t^2}{rst}+\dfrac{t^2r^2}{rst}\\ =\dfrac{r^2s^2+s^2t^2+t^2r^2}{rst}$

$\text{Let x be }(rs + st + tr)^2\\ x=(rs + st + tr)^2 = r^2s^2+s^2t^2+t^2r^2+2rs^2t+2r^2st+2rst^2\\ \therefore r^2s^2+s^2t^2+t^2r^2=(rs + st + tr)^2 - 2rst(s+r+t)$

$\text{Substitute the expression.} \\\dfrac{r^2s^2+s^2t^2+t^2r^2}{rst}\\=\dfrac{(rs+st+tr)^2-2rst(r+s+t)}{rst}$

$\text{Substitute the values.}\\ r+s+t = \dfrac{-(-5)}{1}=5\\ rst = \dfrac{-(-9)}{1}=9\\ rs+st+tr = \dfrac{6}{1}= 6$

$\dfrac{(rs+st+tr)^2-2rst(r+s+t)}{rst}\\=\dfrac{6^2-2(9)(5)}{9}\\ =4-10\\ =-6$

$\therefore \dfrac{rs}{t}+\dfrac{st}{r}+\dfrac{tr}{s}= -6$

The (sum of) interior angles of a square measure 360°

\begin{array}{rll} 2x-8&=&6-5x\\

 7x&=&14\\

x&=&2

\end{array}

$\dfrac{m}{x}+q=N\\ \dfrac{9}{2}+q=\dfrac{9}{5}\\ q = \dfrac{9}{5}-\dfrac{9}{2}\\ \;\;=\dfrac{18-45}{10}\\\;\;=\dfrac{-27}{10}\\\;\;=-2\dfrac{7}{10}$

$\text{If you want to make }\dfrac{a}{b} \text{ , type }\mathtt a/\mathtt b\text{ in the calculator on this website.}$

Oops I was wrong in the last bit :P

Area of a square = (side length)²

x = atan (0.4557) $\approx 0.4276 \text{ radians or }24.4988^{\circ}$

Further steps on asinus's last step.

$\huge\color{blue}y=\dfrac{x-4\pm\sqrt{(4-x)^2+40}}{2}$

Oops is it too big xD

$\huge\color{blue}y=\dfrac{x-4\pm\sqrt{-x^2+8x+24}}{2}$

9.47 x 5 = 47.35

Use the calculator!! It's just located at the home page of this website.