-2(u+7)(-u+5)=0

Solution for -2(u+7)(-u+5)=0 equation:

-2(u+7)(-u+5)=0

We add all the numbers together, and all the variables

-2(u+7)(-1u+5)=0

We multiply parentheses ..

-2(-1u^2+5u-7u+35)=0

We multiply parentheses

2u^2-10u+14u-70=0

We add all the numbers together, and all the variables

2u^2+4u-70=0

a = 2; b = 4; c = -70;
Δ = b2-4ac
Δ = 42-4·2·(-70)
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-24}{2*2}=\frac{-28}{4}
=-7
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+24}{2*2}=\frac{20}{4}
=5
$