r2+7r+9=0

Solution for r2+7r+9=0 equation:

r2+7r+9=0

We add all the numbers together, and all the variables

r^2+7r+9=0

a = 1; b = 7; c = +9;
Δ = b2-4ac
Δ = 72-4·1·9
Δ = 13
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{-(7)-\sqrt{13}}{2*1}=\frac{-7-\sqrt{13}}{2}
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+\sqrt{13}}{2*1}=\frac{-7+\sqrt{13}}{2}
$