Question

if the nth term an A.P is 7-3n , find the sum of 25 th term

Answer 1

by putting 1,2,3 you get the Sn 1,2,3 then subtract S2- S1 to find a then subtract S3-S2 to find A2 then subtract A2-A1 to find d then by using. Sn=n/2(2a +(n-1)d you can find 25 th term

Answer 2

$25th \: term = 7 - 3 \times 25 \\ = 7 - 75 = - 68$
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