(4x+8)(2x)=280

Solution for (4x+8)(2x)=280 equation:

(4x+8)(2x)=280

We move all terms to the left:

(4x+8)(2x)-(280)=0

We multiply parentheses

8x^2+16x-280=0

a = 8; b = 16; c = -280;
Δ = b2-4ac
Δ = 162-4·8·(-280)
Δ = 9216
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9216}=96$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-96}{2*8}=\frac{-112}{16}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+96}{2*8}=\frac{80}{16}
=5
$