-9a^2+27a-20=0

Solution for -9a^2+27a-20=0 equation:

-9a^2+27a-20=0

a = -9; b = 27; c = -20;
Δ = b2-4ac
Δ = 272-4·(-9)·(-20)
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(27)-3}{2*-9}=\frac{-30}{-18}
=1+2/3
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(27)+3}{2*-9}=\frac{-24}{-18}
=1+1/3
$