14400=1200p-9p^2

Solution for 14400=1200p-9p^2 equation:

14400=1200p-9p^2

We move all terms to the left:

14400-(1200p-9p^2)=0

We get rid of parentheses

9p^2-1200p+14400=0

a = 9; b = -1200; c = +14400;
Δ = b2-4ac
Δ = -12002-4·9·14400
Δ = 921600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{921600}=960$
$p_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-1200)-960}{2*9}=\frac{240}{18}
=13+1/3
$
$p_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1200)+960}{2*9}=\frac{2160}{18}
=120
$