I tried to graph y = x^2 - 4x + 4 and ended up with an x-intercept of -2 (the y-intercept is 4). However, according to wolfram, the x-intercept should be 2. Who is correct: me or the website?

Question

I tried to graph y = x^2 - 4x + 4 and ended up with an x-intercept of -2 (the y-intercept is 4). However, according to wolfram, the x-intercept should be 2. Who is correct: me or the website?

Answer 1

y = x^2 - 4x+ 4

= (x - 2)^2

for x-intercept, let y = 0
(x-2)^2 = 0
x-2 = 0
x = 2

we have a double root at x = 2 , ( x=2 or x=2)

see Wolfram:
http://www.wolframalpha.com/input/?i=plot+y+%3D+x%5E2+-+4x+%2B+4

Usually , I would put my money on Wolfram.