15.7=12.56r^2

Solution for 15.7=12.56r^2 equation:

15.7=12.56r^2

We move all terms to the left:

15.7-(12.56r^2)=0

We get rid of parentheses

-12.56r^2+15.7=0

a = -12.56; b = 0; c = +15.7;
Δ = b2-4ac
Δ = 02-4·(-12.56)·15.7
Δ = 788.768
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-\sqrt{788.768}}{2*-12.56}=\frac{0-\sqrt{788.768}}{-25.12}
=-\frac{\sqrt{}}{-25.12}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{788.768}}{2*-12.56}=\frac{0+\sqrt{788.768}}{-25.12}
=\frac{\sqrt{}}{-25.12}
$