The sum of first 9 terms of an arithmetic sequence and the sum of next 8 terms are equal. If its
common difference is 5.
a) How many times of the common difference will be the difference between 10th and first
terms of this sequence?
b) What is the 9th term of this sequence?
c) What is the sum of first 17 terms of this sequence?
Answers
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Step-by-step explanation:
a1+a20=88
a.
a2+a19
=(a1+d)+(a20−d)
=a1+a20
=88
b.
a10+a11=a1+9d+a20−9d
42+a11=a1+a20
∴a11=88−42=46
c.
d=a11−a10
=46−42=4
d.
a10=a+9d
a=42−9(4)
∴a=6
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