0=-0.0045X^2+1.2x+15

Solution for 0=-0.0045X^2+1.2x+15 equation:

0=-0.0045X^2+1.2X+15

We move all terms to the left:

0-(-0.0045X^2+1.2X+15)=0

We add all the numbers together, and all the variables

-(-0.0045X^2+1.2X+15)=0

We get rid of parentheses

0.0045X^2-1.2X-15=0

a = 0.0045; b = -1.2; c = -15;
Δ = b2-4ac
Δ = -1.22-4·0.0045·(-15)
Δ = 1.71
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{-(-1.2)-\sqrt{1.71}}{2*0.0045}=\frac{1.2-\sqrt{1.71}}{0.009}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.2)+\sqrt{1.71}}{2*0.0045}=\frac{1.2+\sqrt{1.71}}{0.009}
$