6.25=r2

Solution for 6.25=r2 equation:

6.25=r2

We move all terms to the left:

6.25-(r2)=0

We add all the numbers together, and all the variables

-1r^2+6.25=0

a = -1; b = 0; c = +6.25;
Δ = b2-4ac
Δ = 02-4·(-1)·6.25
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-5}{2*-1}=\frac{-5}{-2}
=2+1/2
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+5}{2*-1}=\frac{5}{-2}
=-2+1/2
$