2x(5x-x)=72

Solution for 2x(5x-x)=72 equation:

2x(5x-x)=72

We move all terms to the left:

2x(5x-x)-(72)=0

We add all the numbers together, and all the variables

2x(+4x)-72=0

We multiply parentheses

8x^2-72=0

a = 8; b = 0; c = -72;
Δ = b2-4ac
Δ = 02-4·8·(-72)
Δ = 2304
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2304}=48$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-48}{2*8}=\frac{-48}{16}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+48}{2*8}=\frac{48}{16}
=3
$