The common difference of an AP is -2,find its sum,its last term is _10
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Answer:
l=a+(n-1)d
10=a +(10-1)(-2)
10=a +9(-2)
10=a-18
10+18=2a
2a=28
Sn=n/2[a+(n-1)d]
Sn=10/2 [28+(10-1)(-2)]
Sn=5[28-18]
Sn=5x10
Sn=50
therefore the sum of ap is 50 .
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