0=-r^2-4r+1760

Solution for 0=-r^2-4r+1760 equation:

0=-r^2-4r+1760

We move all terms to the left:

0-(-r^2-4r+1760)=0

We add all the numbers together, and all the variables

-(-r^2-4r+1760)=0

We get rid of parentheses

r^2+4r-1760=0

a = 1; b = 4; c = -1760;
Δ = b2-4ac
Δ = 42-4·1·(-1760)
Δ = 7056
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{7056}=84$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-84}{2*1}=\frac{-88}{2}
=-44
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+84}{2*1}=\frac{80}{2}
=40
$