X2-16x+9=0

Solution for X2-16x+9=0 equation:

X2-16X+9=0

We add all the numbers together, and all the variables

X^2-16X+9=0

a = 1; b = -16; c = +9;
Δ = b2-4ac
Δ = -162-4·1·9
Δ = 220
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{220}=\sqrt{4*55}=\sqrt{4}*\sqrt{55}=2\sqrt{55}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-16)-2\sqrt{55}}{2*1}=\frac{16-2\sqrt{55}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-16)+2\sqrt{55}}{2*1}=\frac{16+2\sqrt{55}}{2}
$