21r^2+73r+56=0

Solution for 21r^2+73r+56=0 equation:

21r^2+73r+56=0

a = 21; b = 73; c = +56;
Δ = b2-4ac
Δ = 732-4·21·56
Δ = 625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{625}=25$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(73)-25}{2*21}=\frac{-98}{42}
=-2+1/3
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(73)+25}{2*21}=\frac{-48}{42}
=-1+1/7
$