(x+11)(x-2.5)=0

Solution for (x+11)(x-2.5)=0 equation:

(x+11)(x-2.5)=0

We multiply parentheses ..

(+x^2-2.5x+11x-27.5)=0

We get rid of parentheses

x^2-2.5x+11x-27.5=0

We add all the numbers together, and all the variables

x^2+8.5x-27.5=0

a = 1; b = 8.5; c = -27.5;
Δ = b2-4ac
Δ = 8.52-4·1·(-27.5)
Δ = 182.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8.5)-\sqrt{182.25}}{2*1}=\frac{-8.5-\sqrt{182.25}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8.5)+\sqrt{182.25}}{2*1}=\frac{-8.5+\sqrt{182.25}}{2}
$