Y=-x^2+10x-4

Solution for Y=-x^2+10x-4 equation:

=-Y^2+10Y-4

We move all terms to the left:

-(-Y^2+10Y-4)=0

We get rid of parentheses

Y^2-10Y+4=0

a = 1; b = -10; c = +4;
Δ = b2-4ac
Δ = -102-4·1·4
Δ = 84
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:

$\sqrt{\Delta}=\sqrt{84}=\sqrt{4*21}=\sqrt{4}*\sqrt{21}=2\sqrt{21}$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{21}}{2*1}=\frac{10-2\sqrt{21}}{2}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{21}}{2*1}=\frac{10+2\sqrt{21}}{2}
$