-3x^2+5x+6.25=0

Solution for -3x^2+5x+6.25=0 equation:

-3x^2+5x+6.25=0

a = -3; b = 5; c = +6.25;
Δ = b2-4ac
Δ = 52-4·(-3)·6.25
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-10}{2*-3}=\frac{-15}{-6}
=2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+10}{2*-3}=\frac{5}{-6}
=-5/6
$