if a,b,c are distinct positive real in H.P then the value of the expression b+a/b-a + b+c/b-c is

Note that a harmonic progression is a progression in which the reciprocal of the terms are in arithmetic progression.For example, the following series is in harmonic progression.     12, 14, 16,18,...Note that the reciprocal of the terms are 2, 4, 6, 8,... which is in arithmetic progression.Now it is given that a, b, c are in harmonic progression.This implies that 1a, 1b, 1c are in arithmetic progression.So twice the middle term equals the sum of extreme terms.      21b=1a+1c           2b=a+cac           b2=aca+c              b=2aca+c        .....(1)It is required to find the value of the expression.          b+ab-a+b+cb-c  Apply componendo and dividendo          = b+a+b-ab+a-b-a+b+c+b-cb+c-b-c          = b+a+b-ab+a-b+a+b+c+b-cb+c-b+c         = 2b2a+2b2c         = b1a+1c        = ba+cacPut the value from (1) to get,        b+ab-a+b+cb-c= 2aca+ca+cac                                  = 2Thus the required value is 2

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.          b+a/b-a + b+c/b-c 
  1. Applying componendo and dividendo
  2. ​b+a+b-a/b+a-b+a + b+c+b-c/b+c-b+c
  3. 2b/2a + 2b/2c = bc + ba/ac 
  4. = b (a+c)/ac
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