-4.9t^2+15t+7=0

Solution for -4.9t^2+15t+7=0 equation:

-4.9t^2+15t+7=0

a = -4.9; b = 15; c = +7;
Δ = b2-4ac
Δ = 152-4·(-4.9)·7
Δ = 362.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-\sqrt{362.2}}{2*-4.9}=\frac{-15-\sqrt{362.2}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+\sqrt{362.2}}{2*-4.9}=\frac{-15+\sqrt{362.2}}{-9.8}
$