4x(x+8)=15

Solution for 4x(x+8)=15 equation:

4x(x+8)=15

We move all terms to the left:

4x(x+8)-(15)=0

We multiply parentheses

4x^2+32x-15=0

a = 4; b = 32; c = -15;
Δ = b2-4ac
Δ = 322-4·4·(-15)
Δ = 1264
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:

$\sqrt{\Delta}=\sqrt{1264}=\sqrt{16*79}=\sqrt{16}*\sqrt{79}=4\sqrt{79}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(32)-4\sqrt{79}}{2*4}=\frac{-32-4\sqrt{79}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(32)+4\sqrt{79}}{2*4}=\frac{-32+4\sqrt{79}}{8}
$