86=4t^2

Solution for 86=4t^2 equation:

86=4t^2

We move all terms to the left:

86-(4t^2)=0

a = -4; b = 0; c = +86;
Δ = b2-4ac
Δ = 02-4·(-4)·86
Δ = 1376
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:

$\sqrt{\Delta}=\sqrt{1376}=\sqrt{16*86}=\sqrt{16}*\sqrt{86}=4\sqrt{86}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{86}}{2*-4}=\frac{0-4\sqrt{86}}{-8}
=-\frac{4\sqrt{86}}{-8}
=-\frac{\sqrt{86}}{-2}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{86}}{2*-4}=\frac{0+4\sqrt{86}}{-8}
=\frac{4\sqrt{86}}{-8}
=\frac{\sqrt{86}}{-2}
$