Question

If an = 5+4n find sn​

Answer 1

Step-by-step explanation:

So nd =4n implying d =4 and a-d=1 implying a=5. That will be 15×33 = 495. Since nth term is 4n+1, so first term is 5 ( put n=1) and 15th term is 61 ( n=15). Sum = 15/2[5+61] = 495.

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