-2(u-7)(-u+9)=0

Solution for -2(u-7)(-u+9)=0 equation:

-2(u-7)(-u+9)=0

We add all the numbers together, and all the variables

-2(u-7)(-1u+9)=0

We multiply parentheses ..

-2(-1u^2+9u+7u-63)=0

We multiply parentheses

2u^2-18u-14u+126=0

We add all the numbers together, and all the variables

2u^2-32u+126=0

a = 2; b = -32; c = +126;
Δ = b2-4ac
Δ = -322-4·2·126
Δ = 16
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16}=4$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-32)-4}{2*2}=\frac{28}{4}
=7
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-32)+4}{2*2}=\frac{36}{4}
=9
$