40t^2-90=0

Solution for 40t^2-90=0 equation:

40t^2-90=0

a = 40; b = 0; c = -90;
Δ = b2-4ac
Δ = 02-4·40·(-90)
Δ = 14400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{14400}=120$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-120}{2*40}=\frac{-120}{80}
=-1+1/2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+120}{2*40}=\frac{120}{80}
=1+1/2
$