x(x+1)=1620

Solution for x(x+1)=1620 equation:

x(x+1)=1620

We move all terms to the left:

x(x+1)-(1620)=0

We multiply parentheses

x^2+x-1620=0

a = 1; b = 1; c = -1620;
Δ = b2-4ac
Δ = 12-4·1·(-1620)
Δ = 6481
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{-(1)-\sqrt{6481}}{2*1}=\frac{-1-\sqrt{6481}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{6481}}{2*1}=\frac{-1+\sqrt{6481}}{2}
$