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Question
Find the value of a25 – a15 for the AP: 6, 9, 12, 15, ………..
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Solution
a = 6, d = 3 ;
a25 = 6 + 24(3) = 78
a15 = 6 + 14(3) = 48 ;
∴ a25 – a15 = 78 – 48
= 30
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