Y=x2-4x-2

Solution for Y=x2-4x-2 equation:

=Y2-4Y-2

We move all terms to the left:

-(Y2-4Y-2)=0

We add all the numbers together, and all the variables

-(+Y^2-4Y-2)=0

We get rid of parentheses

-Y^2+4Y+2=0

We add all the numbers together, and all the variables

-1Y^2+4Y+2=0

a = -1; b = 4; c = +2;
Δ = b2-4ac
Δ = 42-4·(-1)·2
Δ = 24
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{24}=\sqrt{4*6}=\sqrt{4}*\sqrt{6}=2\sqrt{6}$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-2\sqrt{6}}{2*-1}=\frac{-4-2\sqrt{6}}{-2}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+2\sqrt{6}}{2*-1}=\frac{-4+2\sqrt{6}}{-2}
$