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

Solution for 4(u+9)(-u-1)=0 equation:

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

4(-1u^2-1u-9u-9)=0

We multiply parentheses

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

We add all the numbers together, and all the variables

-4u^2-40u-36=0

a = -4; b = -40; c = -36;
Δ = b2-4ac
Δ = -402-4·(-4)·(-36)
Δ = 1024
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1024}=32$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-32}{2*-4}=\frac{8}{-8}
=-1
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+32}{2*-4}=\frac{72}{-8}
=-9
$