If (b – c)2, (c – a)2, (a – b)2 are in A.P., then show that:
are in A.P.
[Hint: Add ab + bc + ca — a2 — b2 — c2 to each term or let
= b — c,
= c— a,
= a — b, then
+
+
= 0]
Given: (b – c)2, (c – a)2, (a – b)2 are in A.P
∴ 2(c – a)2 = (b – c)2 + (a – b)2 …(i)
To Prove:
are in AP
or ![]()
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⇒2(b – c)(a – b) = (a – c)(c – a)
⇒2[ab – b2 – ca + cb] = ac – a2 – c2 + ac
⇒2ab – 2b2 – 2ac + 2cb = 2ac – a2 – c2
⇒ a2 + c2 – 4ac = 2b2 – 2ab – 2cb
Adding both sides, a2 + c2, we get
⇒2(a2 + c2) – 4ac = a2 + b2 – 2ab + c2 + b2– 2cb
⇒ 2 (a – c)2 = ( b – a)2 + (b – c)2 which is true from (i)
∴(b – c)2, (c – a)2, (a – b)2 are in A.P
are in AP
Hence Proved
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