-15a^2+6a+9=0

Solution for -15a^2+6a+9=0 equation:

-15a^2+6a+9=0

a = -15; b = 6; c = +9;
Δ = b2-4ac
Δ = 62-4·(-15)·9
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-24}{2*-15}=\frac{-30}{-30}
=1
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+24}{2*-15}=\frac{18}{-30}
=-3/5
$