8) Which term of the A.P 4,11.18.25
is 42 more than its 25th term? Also find sumof it's first 15terms .
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Answer:
Herea=4
d=7
a25=4+24×7
=4+168
=172
172+42=214
an=214
=>214=4+(n-1)7
=>214=4+7n-7
=>214=7n-3
=>217=7n
=>n=31 th
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