x2+25x+66=0.

Solution for x2+25x+66=0. equation:

x2+25x+66=0.

We add all the numbers together, and all the variables

x^2+25x+66=0

a = 1; b = 25; c = +66;
Δ = b2-4ac
Δ = 252-4·1·66
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-19}{2*1}=\frac{-44}{2}
=-22
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+19}{2*1}=\frac{-6}{2}
=-3
$