Answer
 9.14  and  1.86
Step-by-step explanation
x²-11x+17
The first thing is to equate it to zero.
x²-11x+17 = 0
x²-11x = -17
x² - 11x + (11/2)² = -17 + (11/2)²
(x² - 11/2)² = -17 + 121/4
(x - 11/2)² = 13.25
x -11/2 = √13.25 or x - 11/2 = -√13.25 
x = √13.25 + 11/2 x = -√13.25 + 11/2
 = 3.64 + 5.5 = -3.64 + 5.5
 = 9.14  = 1.86