the first term of an A.P.is-5 and the 6 term is 45. find s6
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Answer:
a=-5
a6=45
a+5d =45
-5+5d =45
5d=50
d=10
s6=6/2{2×(-5)+(6-1)10}
s6=3{-10+50}
s6=3(40)
s6=120
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