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91Ó°ÊÓ

Find each sum

7+12+17+.....+(2+5n)

Short Answer

Expert verified

The solution isSn=n2(9+5n)

Step by step solution

01

Given information

7+12+17+.....+(2+5n)

02

Calculation

We have, 7+12+17+.....+(2+5n)

So , a1=7,d=5,an=2+5n

Now use formula,

Sn=n2(a1+an)=n2(7+2+5n)=n2(9+5n)

The sum isSn=n2(9+5n)

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