Question

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?​

Answer 1

Answer:

Answer:

hey mate here is your answer,

Step-by-step explanation:

Hope it helps you

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Answer 2

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