Plugging it in to the quadratic formula
\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)
We have.
\(x = {10 \pm \sqrt{-10^2-4*9} \over 2} = {10 \pm \sqrt{64}\over 2} = {10 \pm 8}\over2\)
So 10 +/- 8 OVER 2 is 18/2 or 1.
Plugging into the equation
9^2 - 90 +9 = 0 = 81 + 9 - 90 = 0
YUP!
1^2 - 10 + 9 = 0 = 1 + 9 - 10 = 10-10 = 0.
YUP!
Great those are our roots.
A quadratic can only have two,
If you don't understand anything feel free to ask!