(2,5+2,5x)*x=200

Solution for (2,5+2,5x)*x=200 equation:

(2.5+2.5x)*x=200

We move all terms to the left:

(2.5+2.5x)*x-(200)=0

We add all the numbers together, and all the variables

(2.5x+2.5)*x-200=0

We multiply parentheses

2x^2+2.5x-200=0

a = 2; b = 2.5; c = -200;
Δ = b2-4ac
Δ = 2.52-4·2·(-200)
Δ = 1606.25
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{-(2.5)-\sqrt{1606.25}}{2*2}=\frac{-2.5-\sqrt{1606.25}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2.5)+\sqrt{1606.25}}{2*2}=\frac{-2.5+\sqrt{1606.25}}{4}
$