1.25l^2-100l-4500=0

Solution for 1.25l^2-100l-4500=0 equation:

1.25l^2-100l-4500=0

a = 1.25; b = -100; c = -4500;
Δ = b2-4ac
Δ = -1002-4·1.25·(-4500)
Δ = 32500
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{32500}=\sqrt{2500*13}=\sqrt{2500}*\sqrt{13}=50\sqrt{13}$
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-100)-50\sqrt{13}}{2*1.25}=\frac{100-50\sqrt{13}}{2.5}
$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-100)+50\sqrt{13}}{2*1.25}=\frac{100+50\sqrt{13}}{2.5}
$