Multiple choice

For the quadratic equation x2 + bx - 9 = 0, where b is an integer, which of the following values is not a possible value for b?

  1. -8

  2. 0

  3. 5

  4. 8
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C Correct answer
AI explanation

Using the condition for real roots of a quadratic equation, the discriminant b squared minus 4ac must be a perfect square greater than or equal to zero. For the given equation, a is 1 and c is negative 9, so the discriminant is b squared plus 36, which must be a perfect square. Testing b equals 5 gives a discriminant of 25 plus 36, which is 61, and this is not a perfect square. Therefore, 5 is not a possible value for b.

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