4=5t^2

Solution for 4=5t^2 equation:

4=5t^2

We move all terms to the left:

4-(5t^2)=0

a = -5; b = 0; c = +4;
Δ = b2-4ac
Δ = 02-4·(-5)·4
Δ = 80
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{80}=\sqrt{16*5}=\sqrt{16}*\sqrt{5}=4\sqrt{5}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{5}}{2*-5}=\frac{0-4\sqrt{5}}{-10}
=-\frac{4\sqrt{5}}{-10}
=-\frac{2\sqrt{5}}{-5}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{5}}{2*-5}=\frac{0+4\sqrt{5}}{-10}
=\frac{4\sqrt{5}}{-10}
=\frac{2\sqrt{5}}{-5}
$