490=4.9t2

Solution for 490=4.9t2 equation:

490=4.9t^2

We move all terms to the left:

490-(4.9t^2)=0

We get rid of parentheses

-4.9t^2+490=0

a = -4.9; b = 0; c = +490;
Δ = b2-4ac
Δ = 02-4·(-4.9)·490
Δ = 9604
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9604}=98$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-98}{2*-4.9}=\frac{-98}{-9.8}
=+10
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+98}{2*-4.9}=\frac{98}{-9.8}
=-10
$