3+21.5x-4.9x^2=0

Solution for 3+21.5x-4.9x^2=0 equation:

3+21.5x-4.9x^2=0

a = -4.9; b = 21.5; c = +3;
Δ = b2-4ac
Δ = 21.52-4·(-4.9)·3
Δ = 521.05
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21.5)-\sqrt{521.05}}{2*-4.9}=\frac{-21.5-\sqrt{521.05}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21.5)+\sqrt{521.05}}{2*-4.9}=\frac{-21.5+\sqrt{521.05}}{-9.8}
$