71=y2

Solution for 71=y2 equation:

71=y2

We move all terms to the left:

71-(y2)=0

We add all the numbers together, and all the variables

-1y^2+71=0

a = -1; b = 0; c = +71;
Δ = b2-4ac
Δ = 02-4·(-1)·71
Δ = 284
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{284}=\sqrt{4*71}=\sqrt{4}*\sqrt{71}=2\sqrt{71}$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{71}}{2*-1}=\frac{0-2\sqrt{71}}{-2}
=-\frac{2\sqrt{71}}{-2}
=-\frac{\sqrt{71}}{-1}
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{71}}{2*-1}=\frac{0+2\sqrt{71}}{-2}
=\frac{2\sqrt{71}}{-2}
=\frac{\sqrt{71}}{-1}
$