(3y+1)(9+y)=0

Solution for (3y+1)(9+y)=0 equation:

(3y+1)(9+y)=0

We add all the numbers together, and all the variables

(3y+1)(y+9)=0

We multiply parentheses ..

(+3y^2+27y+y+9)=0

We get rid of parentheses

3y^2+27y+y+9=0

We add all the numbers together, and all the variables

3y^2+28y+9=0

a = 3; b = 28; c = +9;
Δ = b2-4ac
Δ = 282-4·3·9
Δ = 676
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{676}=26$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-26}{2*3}=\frac{-54}{6}
=-9
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+26}{2*3}=\frac{-2}{6}
=-1/3
$