HEY GUYZ..!! GOOD EVENING TO ALL..!! HERE IS MY QUESTION.. :)
If nth term of an A.P. is (2n+1), what is the sum of its first three terms?
Anonymous:
n=2 2 nd term 2*2+1=5 ..........n=3 3 rd term is 2*3+1=7
s3 = 3+5+7 = 15
tqq
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but u can answer it in answer box na?
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okk :)
hey someone else started answering it ........... thats ok need any more help?do ask me if u have any doubts.......
its ok frnd.. tqq :)
Answers
Answered by
2
Answer:
15
Step-by-step explanation:
Given,nth term of an AP = 2n + 1.
Substitute n = 1,we get
⇒ First term = a₁ = 2(1) + 1
= 3
⇒ Second term = a₂ = 2(2) + 1
= 5
⇒ Third term = a₃ = 2(3) + 1
= 7.
Sum of first 3 three terms = 3 + 5 + 7
= 15.
Note: If it was asked for more number of terms,the apply sum of n terms formula = Sn = (n/2)[2a +(n - 1) * d]
Hope it helps!
tqq so much.. :)
Welcome :-)
okk
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Sir answer my question
Answered by
2
Answer:
15
Step-by-step explanation:
Let n be 1
a1 = 2(1) + 1
a1 = 3
Let n be 2
a(2) = 2(2) + 1
a(2) = 5
Let n be 3
a3 = 2(3) + 1
a3 = 7
Sum of first three terms = 3/2[a1 + a3]
Sum of first three terms = 3/2[3+7]
Sum of first three terms = 30/2
Sum of first three terms = 15
:)
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