3. In the A.P: 7.14.21. .... how many terms are to be considered for getting sum
57402
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Answer:
n=127th term
Step-by-step explanation:
the common difference is 7 as 14-7=7
a=7
given the sum is 57402 so we use the formula
sum of n terms = n/2(2a+(n-1)d)
57402=n/2 (14+7n-7)
57402=n/2 (7+7n)
114804= 7n+7n^2
7n^2+7n-114804=0
n=127th term
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