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If x = a + 1a and y = a –1a then x4 + y4 - 2x²y² = ?

If x = a + 1a and y = a –1a then x4 + y4 - 2x²y² = ? Correct Answer 16

x4 + y4 - 2x2y2= (x2  - y2)2= (2a .  2/a)2      [যেহেতু, x+y= 2a এবং  x-y=2/a]= 42=16

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If x = a+ 1a and y = a-1a then x4+y4-2x2y2=?
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