-4.9x^2+14x+2.5=0

Solution for -4.9x^2+14x+2.5=0 equation:

-4.9x^2+14x+2.5=0

a = -4.9; b = 14; c = +2.5;
Δ = b2-4ac
Δ = 142-4·(-4.9)·2.5
Δ = 245
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:

$\sqrt{\Delta}=\sqrt{245}=\sqrt{49*5}=\sqrt{49}*\sqrt{5}=7\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-7\sqrt{5}}{2*-4.9}=\frac{-14-7\sqrt{5}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+7\sqrt{5}}{2*-4.9}=\frac{-14+7\sqrt{5}}{-9.8}
$