4.9*t^2+4*t-760=0

Solution for 4.9*t^2+4*t-760=0 equation:

4.9t^2+4t-760=0

a = 4.9; b = 4; c = -760;
Δ = b2-4ac
Δ = 42-4·4.9·(-760)
Δ = 14912
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:

$\sqrt{\Delta}=\sqrt{14912}=\sqrt{64*233}=\sqrt{64}*\sqrt{233}=8\sqrt{233}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-8\sqrt{233}}{2*4.9}=\frac{-4-8\sqrt{233}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+8\sqrt{233}}{2*4.9}=\frac{-4+8\sqrt{233}}{9.8}
$