104=l(l-5)

Solution for 104=l(l-5) equation:

104=l(l-5)

We move all terms to the left:

104-(l(l-5))=0


We calculate terms in parentheses: -(l(l-5)), so:

l(l-5)

We multiply parentheses

l^2-5l

Back to the equation:

-(l^2-5l)


We get rid of parentheses

-l^2+5l+104=0

We add all the numbers together, and all the variables

-1l^2+5l+104=0

a = -1; b = 5; c = +104;
Δ = b2-4ac
Δ = 52-4·(-1)·104
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-21}{2*-1}=\frac{-26}{-2}
=+13
$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+21}{2*-1}=\frac{16}{-2}
=-8
$