5(2b+6)b=4

Solution for 5(2b+6)b=4 equation:

5(2b+6)b=4

We move all terms to the left:

5(2b+6)b-(4)=0

We multiply parentheses

10b^2+30b-4=0

a = 10; b = 30; c = -4;
Δ = b2-4ac
Δ = 302-4·10·(-4)
Δ = 1060
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:

$\sqrt{\Delta}=\sqrt{1060}=\sqrt{4*265}=\sqrt{4}*\sqrt{265}=2\sqrt{265}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-2\sqrt{265}}{2*10}=\frac{-30-2\sqrt{265}}{20}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+2\sqrt{265}}{2*10}=\frac{-30+2\sqrt{265}}{20}
$