750=2t+4.9t^2

Solution for 750=2t+4.9t^2 equation:

750=2t+4.9t^2

We move all terms to the left:

750-(2t+4.9t^2)=0

We get rid of parentheses

-4.9t^2-2t+750=0

a = -4.9; b = -2; c = +750;
Δ = b2-4ac
Δ = -22-4·(-4.9)·750
Δ = 14704
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{14704}=\sqrt{16*919}=\sqrt{16}*\sqrt{919}=4\sqrt{919}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2)-4\sqrt{919}}{2*-4.9}=\frac{2-4\sqrt{919}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2)+4\sqrt{919}}{2*-4.9}=\frac{2+4\sqrt{919}}{-9.8}
$