Reciprocal-square evaluation leading to a new equation

Reciprocal-square evaluation leading to a new equation

IB Year 6 | Grade 12

The roots of the quadratic equation \(x^2+x-3=0\) are \(\alpha\) and \(\beta\).

  1. Write down the values of \(\alpha+\beta\) and of \(\alpha\beta\).
  2. Without solving the equation, find the value of each of the following.
    1. \(\dfrac{1}{\alpha^2}+\dfrac{1}{\beta^2}\)
    2. \(\left(\alpha-\dfrac{2}{\beta^2}\right)\left(\beta-\dfrac{2}{\alpha^2}\right)\)
  3. Determine the quadratic equation with integer coefficients which has roots \(\alpha-\dfrac{2}{\beta^2}\) and \(\beta-\dfrac{2}{\alpha^2}\).

Solution:

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Answer:(a) \(-1,\ -3\) (b)(i) \(\frac{7}{9}\) (ii) \(-\frac{29}{9}\) (c) \(9x^2+23x-29=0\)

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