(7b+1)(2b+1)=0

Solution for (7b+1)(2b+1)=0 equation:

(7b+1)(2b+1)=0

We multiply parentheses ..

(+14b^2+7b+2b+1)=0

We get rid of parentheses

14b^2+7b+2b+1=0

We add all the numbers together, and all the variables

14b^2+9b+1=0

a = 14; b = 9; c = +1;
Δ = b2-4ac
Δ = 92-4·14·1
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-5}{2*14}=\frac{-14}{28}
=-1/2
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+5}{2*14}=\frac{-4}{28}
=-1/7
$