If π‘Ž be the arithmetic mean between 𝑏 and 𝑐, 𝑏 be the geometric mean between 𝑐 and π‘Ž then prove that 𝑐 is the harmonic mean between π‘Ž and 𝑏.

engausidarb

engausidarb

Answered question

2022-09-06

If π‘Ž be the arithmetic mean between 𝑏 and 𝑐, 𝑏 be the geometric mean between 𝑐 and π‘Ž then prove that 𝑐 is the harmonic mean between π‘Ž and 𝑏.

Answer & Explanation

Yadira Mcdowell

Yadira Mcdowell

Beginner2022-09-07Added 13 answers

(AM) a = b + c 2
(GM) b = a c
(from AM,(1)) 2 a = b + c
(from GMΒ  b = a c ) 2 a = a c + a
a = a c
a = c ⟹ a = c
Put a = c in (1)
2 a = b + a ⟹ b = a
So a = b = c, so c is the harmonic mean between a and b as:
(sinceΒ  a = b = c ) 2 c = 1 a + 1 b
reinzogoq

reinzogoq

Beginner2022-09-08Added 2 answers

By Multiplying eqn(1) by β€˜b’ and replacing b2 by eqn (2) in (1) we get,
ab = b ((b+c)/2)
ab = (b2 +bc )/2
ab = (ac +bc )/2
ab = c(a+b) )/2
c = 2ab /(a+b)
hence c is the haromonic mean of a and b

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