3=l2-1l+2

Solution for 3=l2-1l+2 equation:

3=l2-1l+2

We move all terms to the left:

3-(l2-1l+2)=0

We add all the numbers together, and all the variables

-(+l^2-1l+2)+3=0

We get rid of parentheses

-l^2+1l-2+3=0

We add all the numbers together, and all the variables

-1l^2+l+1=0

a = -1; b = 1; c = +1;
Δ = b2-4ac
Δ = 12-4·(-1)·1
Δ = 5
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$l_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-\sqrt{5}}{2*-1}=\frac{-1-\sqrt{5}}{-2}
$
$l_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{5}}{2*-1}=\frac{-1+\sqrt{5}}{-2}
$