D(x)=x^2-16x+4

Solution for D(x)=x^2-16x+4 equation:

(D)=D^2-16D+4

We move all terms to the left:

(D)-(D^2-16D+4)=0

We get rid of parentheses

-D^2+D+16D-4=0

We add all the numbers together, and all the variables

-1D^2+17D-4=0

a = -1; b = 17; c = -4;
Δ = b2-4ac
Δ = 172-4·(-1)·(-4)
Δ = 273
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$D_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$D_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$D_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-\sqrt{273}}{2*-1}=\frac{-17-\sqrt{273}}{-2}
$
$D_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+\sqrt{273}}{2*-1}=\frac{-17+\sqrt{273}}{-2}
$