x(x-3.2)=86

Solution for x(x-3.2)=86 equation:

x(x-3.2)=86

We move all terms to the left:

x(x-3.2)-(86)=0

We multiply parentheses

x^2-3.2x-86=0

a = 1; b = -3.2; c = -86;
Δ = b2-4ac
Δ = -3.22-4·1·(-86)
Δ = 354.24
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3.2)-\sqrt{354.24}}{2*1}=\frac{3.2-\sqrt{354.24}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.2)+\sqrt{354.24}}{2*1}=\frac{3.2+\sqrt{354.24}}{2}
$