which term of the A.P 4,9,14... is 89? also find the sum of 4+9+15...+89
Answers
Answered by
6
sn=n÷2(a+l)
an=,a+(n-1)d
89= 4+(n-1)5
89-4=(n-1)5
85÷5=n-1
17+1=n
n=18
sn=18÷2(4+89)
=9×93
=838
an=,a+(n-1)d
89= 4+(n-1)5
89-4=(n-1)5
85÷5=n-1
17+1=n
n=18
sn=18÷2(4+89)
=9×93
=838
Answered by
0
Answer:
total term of AP = 18
then sum of the AP =
18 /2(2×4 + (18-1)×5)
= 9 (8+85)
= 9 × 93 = 837
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