77=x*x

Solution for 77=x*x equation:

77=x*x

We move all terms to the left:

77-(x*x)=0

We add all the numbers together, and all the variables

-(+x*x)+77=0

We get rid of parentheses

-x*x+77=0

Wy multiply elements

-1x^2+77=0

a = -1; b = 0; c = +77;
Δ = b2-4ac
Δ = 02-4·(-1)·77
Δ = 308
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{308}=\sqrt{4*77}=\sqrt{4}*\sqrt{77}=2\sqrt{77}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-2\sqrt{77}}{2*-1}=\frac{0-2\sqrt{77}}{-2}
=-\frac{2\sqrt{77}}{-2}
=-\frac{\sqrt{77}}{-1}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+2\sqrt{77}}{2*-1}=\frac{0+2\sqrt{77}}{-2}
=\frac{2\sqrt{77}}{-2}
=\frac{\sqrt{77}}{-1}
$