P=-n^2+70n

Solution for P=-n^2+70n equation:

=-P^2+70P

We move all terms to the left:

-(-P^2+70P)=0

We get rid of parentheses

P^2-70P=0

a = 1; b = -70; c = 0;
Δ = b2-4ac
Δ = -702-4·1·0
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$P_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-70)-70}{2*1}=\frac{0}{2}
=0
$
$P_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-70)+70}{2*1}=\frac{140}{2}
=70
$