For the equation y = x² - 4x + 4 the variables are a=1, b=-4, c=4

y-intercept (where x = 0):
    y = 1(0)² - 4(0) + 4 = 4

vertex format (completing the square):
    y = x² - 4x + 4 + 4 - 4 => y = (x - 2)² (vertex is (2, 0))

x-intercept format ("factored"):

Find factors of 4 (c) whose sum is -4 (b)

Pairwise factors of 4*

Candidate	Factor 1	Factor 2	Sum
1	-1	-4	-5
2	-2	-2	-4

* Notice that only negative terms were considered, since the b term (-4) is negative but the c term (4) is positive.

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