17r-4r^2=15

Solution for 17r-4r^2=15 equation:

17r-4r^2=15

We move all terms to the left:

17r-4r^2-(15)=0

a = -4; b = 17; c = -15;
Δ = b2-4ac
Δ = 172-4·(-4)·(-15)
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-7}{2*-4}=\frac{-24}{-8}
=+3
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+7}{2*-4}=\frac{-10}{-8}
=1+1/4
$