-0,5(x+2)(x-5)=0

Solution for -0,5(x+2)(x-5)=0 equation:

-0.5(x+2)(x-5)=0

We multiply parentheses ..

-0.5(+x^2-5x+2x-10)=0

We multiply parentheses

-0.5x^2+2.5x-x+5=0

We add all the numbers together, and all the variables

-0.5x^2+1.5x+5=0

a = -0.5; b = 1.5; c = +5;
Δ = b2-4ac
Δ = 1.52-4·(-0.5)·5
Δ = 12.25
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{-(1.5)-\sqrt{12.25}}{2*-0.5}=\frac{-1.5-\sqrt{12.25}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.5)+\sqrt{12.25}}{2*-0.5}=\frac{-1.5+\sqrt{12.25}}{-1}
$