13r^2+2r-11=0

Solution for 13r^2+2r-11=0 equation:

13r^2+2r-11=0

a = 13; b = 2; c = -11;
Δ = b2-4ac
Δ = 22-4·13·(-11)
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-24}{2*13}=\frac{-26}{26}
=-1
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+24}{2*13}=\frac{22}{26}
=11/13
$