300=60x+4.9x^2

Solution for 300=60x+4.9x^2 equation:

300=60x+4.9x^2

We move all terms to the left:

300-(60x+4.9x^2)=0

We get rid of parentheses

-4.9x^2-60x+300=0

a = -4.9; b = -60; c = +300;
Δ = b2-4ac
Δ = -602-4·(-4.9)·300
Δ = 9480
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:

$\sqrt{\Delta}=\sqrt{9480}=\sqrt{4*2370}=\sqrt{4}*\sqrt{2370}=2\sqrt{2370}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-2\sqrt{2370}}{2*-4.9}=\frac{60-2\sqrt{2370}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+2\sqrt{2370}}{2*-4.9}=\frac{60+2\sqrt{2370}}{-9.8}
$