The sum of first 9 terms of an ap is 351 and the sum of first 20 terms is 1770 find the sum of the first n terms
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Step-by-step explanation: a =3 and d=9 explainatiom in photo
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muhseemuneer:
that was very helpful..... but wat is the the sum of the nth term??
Put n/2 (2a +(n-1) d, a=3 d=9
Reply if you want paper explaination
so it will be n/2(6a+9n-9)
ryt??!!
No it will 9n²-3n/2
ok
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