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Question: find the sum of all possible integral values of p for which the equation |x+1/x-3| = p-3 has exactly...

find the sum of all possible integral values of p for which the equation |x+1/x-3| = p-3 has exactly 2 distinct solutions

Answer

21

Explanation

Solution

  1. Split x+1x3=p3\left|x+\frac{1}{x}-3\right|=p-3 into x+1x=px+\frac{1}{x}=p and x+1x=6px+\frac{1}{x}=6-p.

  2. For p3p\ge3, the first equation always gives 2 solutions.

  3. For the second equation to have no solutions, we need 6p<2|6-p|<2 which is true for p(4,8)p\in(4,8).

  4. Also, p=3p=3 makes both branches identical (giving 2 solutions).

  5. Thus, valid integral pp are 3,5,6,73, 5, 6, 7 whose sum equals 21.