An A.P. 5, 12 ,19, ..........has 50 terms. Find its last term . Hence find the sum of its last 15 terms.
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Given A.P is 5,12,19.......505,12,19.......
50 terms
a=5;d=7;n=50
an=a+(n−1)d
an=5+49×7
=5+343=348
Sn=n/2[2a+(n−1)d]
Sum of the last 15 terms
a=348,d=−7,n=15a=348,d=−7,n=15
Sn=n/2[2n+(n−1)d]
S=152[2×348−(14)(−7)]
=152[696+98]
=15×397
=5955
Hope it helps u
Plz mark as brainliest
50 terms
a=5;d=7;n=50
an=a+(n−1)d
an=5+49×7
=5+343=348
Sn=n/2[2a+(n−1)d]
Sum of the last 15 terms
a=348,d=−7,n=15a=348,d=−7,n=15
Sn=n/2[2n+(n−1)d]
S=152[2×348−(14)(−7)]
=152[696+98]
=15×397
=5955
Hope it helps u
Plz mark as brainliest
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