(5u+6)(3-u)=0

Solution for (5u+6)(3-u)=0 equation:

(5u+6)(3-u)=0

We add all the numbers together, and all the variables

(5u+6)(-1u+3)=0

We multiply parentheses ..

(-5u^2+15u-6u+18)=0

We get rid of parentheses

-5u^2+15u-6u+18=0

We add all the numbers together, and all the variables

-5u^2+9u+18=0

a = -5; b = 9; c = +18;
Δ = b2-4ac
Δ = 92-4·(-5)·18
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-21}{2*-5}=\frac{-30}{-10}
=+3
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+21}{2*-5}=\frac{12}{-10}
=-1+1/5
$