Find the sum of the 25 terms of an ap in which the third term is 7 and the 7th term is two more than thrice of its third term
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we have to find s25=?
a3=7
a7=2+3a3
a7=23
so
a+2d=7
a+6d=23
-4d=-16
d=4
a=-1
then we find the terms of ap a1, a2, a3.....
n=25
then by these we find the sums of ap
a3=7
a7=2+3a3
a7=23
so
a+2d=7
a+6d=23
-4d=-16
d=4
a=-1
then we find the terms of ap a1, a2, a3.....
n=25
then by these we find the sums of ap
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