(80-4x-0.25(x^2))=25

Solution for (80-4x-0.25(x^2))=25 equation:

(80-4x-0.25(x^2))=25

We move all terms to the left:

(80-4x-0.25(x^2))-(25)=0

We get rid of parentheses

-0.25x^2-4x+80-25=0

We add all the numbers together, and all the variables

-0.25x^2-4x+55=0

a = -0.25; b = -4; c = +55;
Δ = b2-4ac
Δ = -42-4·(-0.25)·55
Δ = 71
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{-(-4)-\sqrt{71}}{2*-0.25}=\frac{4-\sqrt{71}}{-0.5}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+\sqrt{71}}{2*-0.25}=\frac{4+\sqrt{71}}{-0.5}
$