6=u*5u

Solution for 6=u*5u equation:

6=u*5u

We move all terms to the left:

6-(u*5u)=0

We add all the numbers together, and all the variables

-(+u*5u)+6=0

We get rid of parentheses

-u*5u+6=0

Wy multiply elements

-5u^2+6=0

a = -5; b = 0; c = +6;
Δ = b2-4ac
Δ = 02-4·(-5)·6
Δ = 120
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{120}=\sqrt{4*30}=\sqrt{4}*\sqrt{30}=2\sqrt{30}$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{30}}{2*-5}=\frac{0-2\sqrt{30}}{-10}
=-\frac{2\sqrt{30}}{-10}
=-\frac{\sqrt{30}}{-5}
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{30}}{2*-5}=\frac{0+2\sqrt{30}}{-10}
=\frac{2\sqrt{30}}{-10}
=\frac{\sqrt{30}}{-5}
$