750=8x+4.9x^2

Solution for 750=8x+4.9x^2 equation:

750=8x+4.9x^2

We move all terms to the left:

750-(8x+4.9x^2)=0

We get rid of parentheses

-4.9x^2-8x+750=0

a = -4.9; b = -8; c = +750;
Δ = b2-4ac
Δ = -82-4·(-4.9)·750
Δ = 14764
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:

$\sqrt{\Delta}=\sqrt{14764}=\sqrt{4*3691}=\sqrt{4}*\sqrt{3691}=2\sqrt{3691}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-2\sqrt{3691}}{2*-4.9}=\frac{8-2\sqrt{3691}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+2\sqrt{3691}}{2*-4.9}=\frac{8+2\sqrt{3691}}{-9.8}
$