8x(5x+5)=16

Solution for 8x(5x+5)=16 equation:

8x(5x+5)=16

We move all terms to the left:

8x(5x+5)-(16)=0

We multiply parentheses

40x^2+40x-16=0

a = 40; b = 40; c = -16;
Δ = b2-4ac
Δ = 402-4·40·(-16)
Δ = 4160
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4160}=\sqrt{64*65}=\sqrt{64}*\sqrt{65}=8\sqrt{65}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(40)-8\sqrt{65}}{2*40}=\frac{-40-8\sqrt{65}}{80}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(40)+8\sqrt{65}}{2*40}=\frac{-40+8\sqrt{65}}{80}
$