60*x+0.15*x^2=200

Solution for 60*x+0.15*x^2=200 equation:

60x+0.15x^2=200

We move all terms to the left:

60x+0.15x^2-(200)=0

a = 0.15; b = 60; c = -200;
Δ = b2-4ac
Δ = 602-4·0.15·(-200)
Δ = 3720
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3720}=\sqrt{4*930}=\sqrt{4}*\sqrt{930}=2\sqrt{930}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(60)-2\sqrt{930}}{2*0.15}=\frac{-60-2\sqrt{930}}{0.3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(60)+2\sqrt{930}}{2*0.15}=\frac{-60+2\sqrt{930}}{0.3}
$