-70+17r=r^2

Solution for -70+17r=r^2 equation:

-70+17r=r^2

We move all terms to the left:

-70+17r-(r^2)=0

determiningTheFunctionDomain
-r^2+17r-70=0

We add all the numbers together, and all the variables

-1r^2+17r-70=0

a = -1; b = 17; c = -70;
Δ = b2-4ac
Δ = 172-4·(-1)·(-70)
Δ = 9
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{9}=3$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-3}{2*-1}=\frac{-20}{-2}
=+10
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+3}{2*-1}=\frac{-14}{-2}
=+7
$