-39=-16x+x^2

Solution for -39=-16x+x^2 equation:

-39=-16x+x^2

We move all terms to the left:

-39-(-16x+x^2)=0

We get rid of parentheses

-x^2+16x-39=0

We add all the numbers together, and all the variables

-1x^2+16x-39=0

a = -1; b = 16; c = -39;
Δ = b2-4ac
Δ = 162-4·(-1)·(-39)
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-10}{2*-1}=\frac{-26}{-2}
=+13
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+10}{2*-1}=\frac{-6}{-2}
=+3
$