Find the sum of first 30 terms of an AP whose nth term is given by 2-3n.
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Answered by
4
an=2-3n
n=1,an1=2-3x1=-1
n=2,an2=2-3x2=2-6=-4
common difference=an2-an1=-4-(-1)=-4+1=-3
Sn=n/2{2a+(n-1)d}
given n=30,first term -1,common difference=-3
s30=30/2{2(-1)+(30-1)-3}
S30=15{-2-87}
S30=-1335
n=1,an1=2-3x1=-1
n=2,an2=2-3x2=2-6=-4
common difference=an2-an1=-4-(-1)=-4+1=-3
Sn=n/2{2a+(n-1)d}
given n=30,first term -1,common difference=-3
s30=30/2{2(-1)+(30-1)-3}
S30=15{-2-87}
S30=-1335
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Answered by
4
an=2-3n
so
a1=2-3*1
=-1
a30=2-3*30
=-88
so
sum=n/2(a1+a30)
=30/2(-1+-88)
=15(-89)
=-1335
so
a1=2-3*1
=-1
a30=2-3*30
=-88
so
sum=n/2(a1+a30)
=30/2(-1+-88)
=15(-89)
=-1335
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