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

Solution for 5(u+7)(-u+1)=0 equation:

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

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

We multiply parentheses

-5u^2+5u-35u+35=0

We add all the numbers together, and all the variables

-5u^2-30u+35=0

a = -5; b = -30; c = +35;
Δ = b2-4ac
Δ = -302-4·(-5)·35
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-30)-40}{2*-5}=\frac{-10}{-10}
=1
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-30)+40}{2*-5}=\frac{70}{-10}
=-7
$