9a^2-20=0

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

9a^2-20=0

a = 9; b = 0; c = -20;
Δ = b2-4ac
Δ = 02-4·9·(-20)
Δ = 720
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{720}=\sqrt{144*5}=\sqrt{144}*\sqrt{5}=12\sqrt{5}$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-12\sqrt{5}}{2*9}=\frac{0-12\sqrt{5}}{18}
=-\frac{12\sqrt{5}}{18}
=-\frac{2\sqrt{5}}{3}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+12\sqrt{5}}{2*9}=\frac{0+12\sqrt{5}}{18}
=\frac{12\sqrt{5}}{18}
=\frac{2\sqrt{5}}{3}
$