P=-0.003x^2+5.25x+495

Solution for P=-0.003x^2+5.25x+495 equation:

=-0.003P^2+5.25P+495

We move all terms to the left:

-(-0.003P^2+5.25P+495)=0

We get rid of parentheses

0.003P^2-5.25P-495=0

a = 0.003; b = -5.25; c = -495;
Δ = b2-4ac
Δ = -5.252-4·0.003·(-495)
Δ = 33.5025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5.25)-\sqrt{33.5025}}{2*0.003}=\frac{5.25-\sqrt{33.5025}}{0.006}
$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5.25)+\sqrt{33.5025}}{2*0.003}=\frac{5.25+\sqrt{33.5025}}{0.006}
$