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Question
If an denotes the nth term of the AP 2, 7, 12, 17, … find the value of (a30 - a20 ).
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Solution
The given AP is 2, 7, 12, 17,………
Here, a = 2 and d = 7 - 2 = 5
∴ a30 - a20
=[ 2 +(30-1) × 5]-[2+(20-1) ×5] [an = a+ (n-1) d]
= 147-97
=50
Hence, the required value is 50.
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