-x2+-16x+28=0

Solution for -x2+-16x+28=0 equation:

-x2+-16x+28=0

We add all the numbers together, and all the variables

-1x^2-16x=0

a = -1; b = -16; c = 0;
Δ = b2-4ac
Δ = -162-4·(-1)·0
Δ = 256
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{256}=16$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-16}{2*-1}=\frac{0}{-2}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+16}{2*-1}=\frac{32}{-2}
=-16
$