11 th term of an arithmetic sequence is 26 .
a) What is the sum of first and 21 st terms of this sequence ?
b) what is the sum of first 21 terms?
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2
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Answer:
hey mate here is your answer,
Step-by-step explanation:
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Answered by
0
Answer:
461
Step-by-step explanation:
d=a_2-a_1=(21)-(16)=5
d=a
2
−a
1
=(21)−(16)=5
a_n=a_1+(n-1)d
a
n
=a
1
+(n−1)d
\text{90th term:}
90th term:
a_{90}=16 + (90-1)(5)
a
90
=16+(90−1)(5)
a_{90}=16 + (89)(5)
a
90
=16+(89)(5)
a_{90}=461
a
90
=461
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