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Which of the following functions describe the graph shown in the below figure?

Graph of y against x from -3 to 3: y is 1 at x = -3, 0 at x = -2, -1 at x = -1, 0 at x = 0, -1 at x = 1, 0 at x = 2 and 1 at x = 3, joined by straight lines

  • A.\(y = ||x| + 1| - 2\)
  • B.\(y = ||x| - 1| - 1\)
  • C.\(y = ||x| + 1| - 1\)
  • D.\(y = ||x - 1| - 1|\)

Answer: B

The graph is \(y = ||x| - 1| - 1\).

Read values off the graph: y = 0 at x = 0, y = -1 at x = ±1, y = 0 at x = ±2 and y = 1 at x = ±3. For this function, \(x = 0\) gives \(|0 - 1| - 1 = 0\); \(x = \pm 1\) gives \(0 - 1 = -1\); \(x = \pm 2\) gives \(1 - 1 = 0\); \(x = \pm 3\) gives \(2 - 1 = 1\). Every point fits.

\(||x| + 1| - 2\) gives -1 at x = 0, and \(||x| + 1| - 1\) gives 0 at x = 0 but never goes negative, so neither has the two dips to -1. \(||x - 1| - 1|\) is never negative at all.

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