For the equation y = x² - 6x + 8 the variables are a=1, b=-6, c=8

y-intercept (where x = 0):
    y = 1(0)² - 6(0) + 8 = 8

vertex format (completing the square):
    y = x² - 6x + 9 + 8 - 9 => y = (x - 3)² - 1 (vertex is (3, -1))

x-intercept format ("factored"):

Find factors of 8 (c) whose sum is -6 (b)

Pairwise factors of 8*

Candidate	Factor 1	Factor 2	Sum
1	-1	-8	-9
2	-2	-4	-6

* Notice that only negative terms were considered, since the b term (-6) is negative but the c term (8) is positive.

The candidate highlighted above gives us the factors.
    y = (x - 4)(x - 2) (using zero product property, the x-intercepts are 4 and 2)

Graph the three versions of the highlighted equations (using Desmos.com here) and confirm they are equivalent. ALSO, confirm that the y- and x-intercepts are correct, as well as the vertex: