10r^2+36=-66r

Solution for 10r^2+36=-66r equation:

10r^2+36=-66r

We move all terms to the left:

10r^2+36-(-66r)=0

We get rid of parentheses

10r^2+66r+36=0

a = 10; b = 66; c = +36;
Δ = b2-4ac
Δ = 662-4·10·36
Δ = 2916
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2916}=54$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(66)-54}{2*10}=\frac{-120}{20}
=-6
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(66)+54}{2*10}=\frac{-12}{20}
=-3/5
$