0=-5x^2+2.5x+7.5

Solution for 0=-5x^2+2.5x+7.5 equation:

0=-5x^2+2.5x+7.5

We move all terms to the left:

0-(-5x^2+2.5x+7.5)=0

We add all the numbers together, and all the variables

-(-5x^2+2.5x+7.5)=0

We get rid of parentheses

5x^2-2.5x-7.5=0

a = 5; b = -2.5; c = -7.5;
Δ = b2-4ac
Δ = -2.52-4·5·(-7.5)
Δ = 156.25
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{156.25}}{2*5}=\frac{2.5-\sqrt{156.25}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.5)+\sqrt{156.25}}{2*5}=\frac{2.5+\sqrt{156.25}}{10}
$