90t^2-640=0

Solution for 90t^2-640=0 equation:

90t^2-640=0

a = 90; b = 0; c = -640;
Δ = b2-4ac
Δ = 02-4·90·(-640)
Δ = 230400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{230400}=480$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-480}{2*90}=\frac{-480}{180}
=-2+2/3
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+480}{2*90}=\frac{480}{180}
=2+2/3
$