The roots of the quadratic equation $x + \frac{2}{x} = 3$ are $\dots$ $(x \neq 0)$.

$x = \dots$ is a solution of the quadratic equation $x^{2} + 7x + 12 = 0$.

Find whether the following equation has real roots. If real roots exist,find them.
$x^{2}+5 \sqrt{5} x-70=0$

Find the roots of the following quadratic equation using the quadratic formula,if they exist: $\frac{1}{x+1} + \frac{2}{x+2} = \frac{4}{x+4}$; $(x \neq -1, -2, -4)$

Find the discriminant of the following quadratic equation: $\sqrt{5} x^{2}-2 \sqrt{2} x-2 \sqrt{5}=0$.

The speed of a motorboat in still water is $9\,km/h$. In a river,it covers $12\,km$ downstream and the same distance upstream in a total time of $3\,hours$. Find the speed of the current of the river. (The speed of the current of the river is less than the speed of the motorboat in still water.) (in $,km/h$)