Question:
Very-Short and Short-Answer Questions
If an denotes the nth term of the AP 2, 7, 12, 17, ... , find the value of (a30 − a20).
Solution:
The given AP is 2, 7, 12, 17, ... .
Here, a = 2 and d = 7 − 2 = 5
$\therefore a_{30}-a_{20}$
$=[2+(30-1) \times 5]-[2+(20-1) \times 5] \quad\left[a_{n}=a+(n-1) d\right]$
$=147-97$
$=50$
Hence, the required value is 50.
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