the sum of first 20 terms of an arithmetic progression is 50 and the sum of next 20 terms is -50 find the sum of first 100 terms of progressions
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Step-by-step explanation:
sn= 20
An is 50
s100 = n/2 * 2a + (n-1) d
=but here it's already given so no need to apply this formula
apply directly sn = n/2 (a+ an)
= 100/2 (
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