3x^2+21x-7.7=0

Solution for 3x^2+21x-7.7=0 equation:

3x^2+21x-7.7=0

a = 3; b = 21; c = -7.7;
Δ = b2-4ac
Δ = 212-4·3·(-7.7)
Δ = 533.4
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)-\sqrt{533.4}}{2*3}=\frac{-21-\sqrt{533.4}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{533.4}}{2*3}=\frac{-21+\sqrt{533.4}}{6}
$