1200=90x^2+60x

Solution for 1200=90x^2+60x equation:

1200=90x^2+60x

We move all terms to the left:

1200-(90x^2+60x)=0

We get rid of parentheses

-90x^2-60x+1200=0

a = -90; b = -60; c = +1200;
Δ = b2-4ac
Δ = -602-4·(-90)·1200
Δ = 435600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{435600}=660$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-660}{2*-90}=\frac{-600}{-180}
=3+1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+660}{2*-90}=\frac{720}{-180}
=-4
$