You either have to use the quadratic equation or factor it to find the roots of the function.
x² - 9x + 9 = 0
x = -(-9) ± √(-9)² - 4(1)(9)
2(1)
x = 9 ± √81 - 36
2
x = 9 ± √45
2
x = 9 ± 3√5
2
x = 4.5 ± 1.5√5

jacksoncelestin

You have to factor. So what multiplies to equal 9 and adds to equal -9? Nothing, so you have to do the quadratic formula setting x to equal that equation. You will have two solutions since the formula is an x squared.