16Hit1600
Advanced MathMediumIdentifying a quadratic with no x-intercepts

Advanced Math practice question

Which of the following equations has a graph in the xy-plane with no x-intercepts?

  1. A. y = x² + 1Correct
  2. B. y = x² − 1
  3. C. y = (x − 1)²
  4. D. y = 1 − x²

Answer: A. y = x² + 1

x² + 1 is at least 1 for every x, so the graph never reaches the x-axis. The others all equal 0 for some x.

Why the other answers are wrong

B. y = x² − 1
x² − 1 = 0 at x = ±1.
C. y = (x − 1)²
(x − 1)² = 0 at x = 1.
D. y = 1 − x²
1 − x² = 0 at x = ±1.

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