5r^2-22r-15=0

Solution for 5r^2-22r-15=0 equation:

5r^2-22r-15=0

a = 5; b = -22; c = -15;
Δ = b2-4ac
Δ = -222-4·5·(-15)
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-22)-28}{2*5}=\frac{-6}{10}
=-3/5
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-22)+28}{2*5}=\frac{50}{10}
=5
$