777=2l^2-5l

Solution for 777=2l^2-5l equation:

777=2l^2-5l

We move all terms to the left:

777-(2l^2-5l)=0

We get rid of parentheses

-2l^2+5l+777=0

a = -2; b = 5; c = +777;
Δ = b2-4ac
Δ = 52-4·(-2)·777
Δ = 6241
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6241}=79$
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-79}{2*-2}=\frac{-84}{-4}
=+21
$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+79}{2*-2}=\frac{74}{-4}
=-18+1/2
$