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Which of the following are factors of \(x^{2} - x - 6\) ?

  • A.\((x + 2), (x - 3)\)
  • B.\((x - 2), (x + 3)\)
  • C.\((x + 1), (x - 6)\)
  • D.\((x - 1), (x + 6)\)

Answer: A

The factors are \((x + 2)\) and \((x - 3)\).

Find two numbers whose product is \(-6\) and whose sum is \(-1\): they are \(+2\) and \(-3\).

\[ x^{2} - x - 6 = (x + 2)(x - 3) \]

Check: \(x^{2} - 3x + 2x - 6 = x^{2} - x - 6\). The pair \((x - 2)(x + 3)\) gives \(x^{2} + x - 6\), with the wrong sign of the middle term, and \((x + 1)(x - 6)\) and \((x - 1)(x + 6)\) give middle terms of \(-5x\) and \(+5x\).

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