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Question
If a, b and c are in A.P. show that 4a, 4b and 4c are in A.P.
Solution
a, b and c are in A.P.
`=>` b – a = c – b
`=>` 2b = a + c
Given terms are 4a, 4b and 4c
Now 4b – 4a = 2(2b – 2a)
= 2(a + c – 2a)
= 2(c – a)
And 4c – 4b = 2(2c – 2b)
= 2(2c – a – c)
= 2(c – a)
Since 4b – 4a = 4c – 4b, the given terms are in A.P.
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