4r^2-26r-140=0

Solution for 4r^2-26r-140=0 equation:

4r^2-26r-140=0

a = 4; b = -26; c = -140;
Δ = b2-4ac
Δ = -262-4·4·(-140)
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{-(-26)-54}{2*4}=\frac{-28}{8}
=-3+1/2
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+54}{2*4}=\frac{80}{8}
=10
$