7.5=r2

Solution for 7.5=r2 equation:

7.5=r2

We move all terms to the left:

7.5-(r2)=0

We add all the numbers together, and all the variables

-1r^2+7.5=0

a = -1; b = 0; c = +7.5;
Δ = b2-4ac
Δ = 02-4·(-1)·7.5
Δ = 30
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{30}}{2*-1}=\frac{0-\sqrt{30}}{-2}
=-\frac{\sqrt{}}{-2}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{30}}{2*-1}=\frac{0+\sqrt{30}}{-2}
=\frac{\sqrt{}}{-2}
$