x(x-3)4=280

Solution for x(x-3)4=280 equation:

x(x-3)4=280

We move all terms to the left:

x(x-3)4-(280)=0

We multiply parentheses

4x^2-12x-280=0

a = 4; b = -12; c = -280;
Δ = b2-4ac
Δ = -122-4·4·(-280)
Δ = 4624
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4624}=68$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-68}{2*4}=\frac{-56}{8}
=-7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+68}{2*4}=\frac{80}{8}
=10
$