9v^2+18v-81=0

Solution for 9v^2+18v-81=0 equation:

9v^2+18v-81=0

a = 9; b = 18; c = -81;
Δ = b2-4ac
Δ = 182-4·9·(-81)
Δ = 3240
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3240}=\sqrt{324*10}=\sqrt{324}*\sqrt{10}=18\sqrt{10}$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(18)-18\sqrt{10}}{2*9}=\frac{-18-18\sqrt{10}}{18}
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(18)+18\sqrt{10}}{2*9}=\frac{-18+18\sqrt{10}}{18}
$