For an arithmetic sequence six terms sum is given 99.sixth term is 39.Find the sum of third term and fourth term. Find the third term and Write the sequence?
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1
sum of third term=-9
sum of fourth term=0
third term=12
sequence=-6,3,12,21,30
sum of fourth term=0
third term=12
sequence=-6,3,12,21,30
Answered by
2
S6=99
Sn=n/2(2a+(n-1)d)
S6=6/2(2a+(6-1)d)
S6=3(2a+5d)
S6=6a+15d=99-eqn1
Sixth term 39
tn=a+(n-1)d
t6=a+5d
a+5d=39-eqn2
From 1 &2
6a+15d=99
a +5d=39
a=-6
d=9
S3=3a+3d=3(-6)+3(9)=9
t1=a+d=3
t2=a+2d=12
t3=a+3d=21
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