3.14r^2+13*3.14r-190=0

Solution for 3.14r^2+13*3.14r-190=0 equation:

3.14r^2+13*3.14r-190=0

Wy multiply elements

3.14r^2+39r-190=0

a = 3.14; b = 39; c = -190;
Δ = b2-4ac
Δ = 392-4·3.14·(-190)
Δ = 3907.4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(39)-\sqrt{3907.4}}{2*3.14}=\frac{-39-\sqrt{3907.4}}{6.28}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(39)+\sqrt{3907.4}}{2*3.14}=\frac{-39+\sqrt{3907.4}}{6.28}
$