(3b+7)(b+3)=0

Solution for (3b+7)(b+3)=0 equation:

(3b+7)(b+3)=0

We multiply parentheses ..

(+3b^2+9b+7b+21)=0

We get rid of parentheses

3b^2+9b+7b+21=0

We add all the numbers together, and all the variables

3b^2+16b+21=0

a = 3; b = 16; c = +21;
Δ = b2-4ac
Δ = 162-4·3·21
Δ = 4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4}=2$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-2}{2*3}=\frac{-18}{6}
=-3
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+2}{2*3}=\frac{-14}{6}
=-2+1/3
$