Question

RITHMETIC PROGRESSIONS
4. How many terms of the AP:9, 17, 25, ...must be taken to give a sum of 636?​

Answer 1

Given...

AP Series 9,17,25..........636

Formula used:-

Sn= n/2{2a+(n-1)d}

To find :-..

Terms =n=???

Solution.....

Sn=636

n=?

a=9

d=a²-a¹

d=17-9

d=8

Sn=n/2{2a+(n-1)d}

636=n/2{2*9+(n-1)8}

636=n/2{18+8n-8}

636=n{9+8n-8}

636=n(1+8n)

636=n+8n²

=> 8n²+n-636=0

Ans ...

Answer 2

Answer:

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