(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)(u+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+21u+18=0

a = 5; b = 21; c = +18;
Δ = b2-4ac
Δ = 212-4·5·18
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$u_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-9}{2*5}=\frac{-30}{10}
=-3
$
$u_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+9}{2*5}=\frac{-12}{10}
=-1+1/5
$