140=r^2

Solution for 140=r^2 equation:

140=r^2

We move all terms to the left:

140-(r^2)=0

We add all the numbers together, and all the variables

-1r^2+140=0

a = -1; b = 0; c = +140;
Δ = b2-4ac
Δ = 02-4·(-1)·140
Δ = 560
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{560}=\sqrt{16*35}=\sqrt{16}*\sqrt{35}=4\sqrt{35}$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-4\sqrt{35}}{2*-1}=\frac{0-4\sqrt{35}}{-2}
=-\frac{4\sqrt{35}}{-2}
=-\frac{2\sqrt{35}}{-1}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+4\sqrt{35}}{2*-1}=\frac{0+4\sqrt{35}}{-2}
=\frac{4\sqrt{35}}{-2}
=\frac{2\sqrt{35}}{-1}
$