The parabola: y = ax2 + bx + c has a vertical line of symmetry at x = 1.
It goes through the point (-1,3) ---> Since the graph has a vertical line of symmetry at x = 1 and since the point (-1,3) is two units to the left of this line, there will be a point with the same y-value two units to the right of this line: (3,3).
Since it goes through the point (2,-2), which is one unit to the right of the vertical line of symmetry, there will be a point with the same y-value one unit to the left of this line: (0,-2).
We only need to use three of these four points in the equation y = ax2 + bx + c:
(-1,3) ---> 3 = a(-1)2 +b(-1) + c ---> 3 = a - b + c (equation #1)
(2,-2) ---> -2 = a(2)2 + b(2) + c ---> -2 = 4a + 2b + c (equation #2)
(3,3) ---> 3 = a(3)2 + b(3) + c ---> 3 = 9a + 3b + c (equation #3)
Combining equations #2 and #1: -2 = 4a + 2b + c ---> -2 = 4a + 2b + c
3 = a - b + c ---> x -1 ---> -3 = -a + b - c
Adding down the columns: -5 = 3a + 3b
Combining equations #3 and #1: 3 = 9a + 3b + c ---> 3 = 9a + 3b + c
3 = a - b + c ---> x -1 ---> -3 = -a + b - c
Adding down the columns: 0 = 8a + 2b ---> 0 = 2a + b
Combing these two new equations: -5 = 3a + 3b ---> -5 = 3a + 3b
0 = 2a + b ---> x -3 ---> 0 = -6a - 3b
Adding down the columns: -5 = -3a ---> a = 5/3
Substituting this value into 0 = 2a + b ---> 0 = 2(5/3) + b ---> 0 = 10/3 + b ---> b = -10/3
Substituting this value into 3 = a - b + c ---> 3 = (5/3) - (-10/3) + c ---> c = -2
Equation: y = ax2 + bx + c ---> y = (5/3)x2 - (10/3)x - 2
This equation has two roots: Using the quadratic formula: x = [ 10 + sqrt(220) ] / 10 and x = [ 10 - sqrt(220) ] / 10
The larger answer is: x = [ 10 + sqrt(220) ] / 10 = 10/10 + sqrt(220)/10 = 1 + sqrt(220) / 10
= 1 + sqrt(220) / sqrt(100) = 1 + sqrt(220/100) = 1 + sqrt(2.20) ---> n = 2.20