-2(u+9)(-u+2)=0

Solution for -2(u+9)(-u+2)=0 equation:

-2(u+9)(-u+2)=0

We add all the numbers together, and all the variables

-2(u+9)(-1u+2)=0

We multiply parentheses ..

-2(-1u^2+2u-9u+18)=0

We multiply parentheses

2u^2-4u+18u-36=0

We add all the numbers together, and all the variables

2u^2+14u-36=0

a = 2; b = 14; c = -36;
Δ = b2-4ac
Δ = 142-4·2·(-36)
Δ = 484
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{484}=22$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-22}{2*2}=\frac{-36}{4}
=-9
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+22}{2*2}=\frac{8}{4}
=2
$