What is the minimum value of for real ?

Answer and explanation

Correct answer: E.

  1. Step 1: Complete the square: .
  2. Step 2: This is .
  3. Step 3: The square is at least , so the minimum is , when .
Answer
.
Why not the others: is the value at and is a value the expression takes (for example at ), but neither is the least; and are below the minimum, since .

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