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Determine the intervals on which \( y = x^2 - 2x - 48 \) is positive. Select all that apply. - \((-\infty,...

Determine the intervals on which \( y = x^2 - 2x - 48 \) is positive.
Select all that apply.
- \((-\infty, -6)\)
- \((-6, \infty)\)
- \((-6,8)\)
- \((-8, \infty)\)
- \((8, \infty)\)

Answer

To find the intervals where \( y = x^2 - 2x - 48 \) is positive, we first find the roots of the equation by setting it to zero:

\( x^2 - 2x - 48 = 0 \)

Using the quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), where \( a = 1 \), \( b = -2 \), and \( c = -48 \):

\( x = \frac{-(-2) \pm \sqrt{(-2)^2 - 4 \cdot 1 \cdot (-48)}}{2 \cdot 1} \)

\( x = \frac{2 \pm \sqrt{4 + 192}}{2} \)

\( x = \frac{2 \pm \sqrt{196}}{2} \)

\( x = \frac{2 \pm 14}{2} \)

\( x = 8 \) or \( x = -6 \)

The roots are \( x = -6 \) and \( x = 8 \). The parabola opens upwards (since the coefficient of \( x^2 \) is positive), so it is positive outside the interval between the roots.

Therefore, the intervals where \( y \) is positive are:

  1. \((-\infty, -6)\)
  2. \((8, \infty)\)

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