0=-0.81t^2+5

Solution for 0=-0.81t^2+5 equation:

0=-0.81t^2+5

We move all terms to the left:

0-(-0.81t^2+5)=0

We add all the numbers together, and all the variables

-(-0.81t^2+5)=0

We get rid of parentheses

0.81t^2-5=0

a = 0.81; b = 0; c = -5;
Δ = b2-4ac
Δ = 02-4·0.81·(-5)
Δ = 16.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{16.2}}{2*0.81}=\frac{0-\sqrt{16.2}}{1.62}
=-\frac{\sqrt{}}{1.62}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{16.2}}{2*0.81}=\frac{0+\sqrt{16.2}}{1.62}
=\frac{\sqrt{}}{1.62}
$