b(5b+5)=262

Solution for b(5b+5)=262 equation:

b(5b+5)=262

We move all terms to the left:

b(5b+5)-(262)=0

We multiply parentheses

5b^2+5b-262=0

a = 5; b = 5; c = -262;
Δ = b2-4ac
Δ = 52-4·5·(-262)
Δ = 5265
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5265}=\sqrt{81*65}=\sqrt{81}*\sqrt{65}=9\sqrt{65}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-9\sqrt{65}}{2*5}=\frac{-5-9\sqrt{65}}{10}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+9\sqrt{65}}{2*5}=\frac{-5+9\sqrt{65}}{10}
$