The nth term tn of an ap is given by tn =4n-5 find the sum of the first 25 terms of the ap
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tn=4n-5
putting n=1,2,3,4,5.......
AP:-1,3,7,11, .........
a=-1 ,d=4
Sn=n/2[2a+(n-1)d]
=25/2[2×-1+(25-1)4]
=25/2[-2+96]
25/2×94
=27×47
now solve
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