3r^2-r-7=0

Solution for 3r^2-r-7=0 equation:

3r^2-r-7=0

We add all the numbers together, and all the variables

3r^2-1r-7=0

a = 3; b = -1; c = -7;
Δ = b2-4ac
Δ = -12-4·3·(-7)
Δ = 85
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{-(-1)-\sqrt{85}}{2*3}=\frac{1-\sqrt{85}}{6}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1)+\sqrt{85}}{2*3}=\frac{1+\sqrt{85}}{6}
$