Question

For an AP the first term is a and the nth term is 1.How would you find the sum of these n terms?​

Answer 1

Answer:

Given,

number of terms in A.P is n.

first term of A.P is a  

1

​  

=a

nth term of A.P is a  

n

​  

=l

let d be the common difference

mth term of an A.P from begning is given by

a  

m

​  

=a+(m−1)d...….eq(1)

for finding the mth term from the end  

the first term becomes a  

1

​  

=l

and the common difference becomes −d

now mth term from last is given by

a  

m

′

​  

=l+(m−1)(−d)….eq(2)

now, we have to find sum of eq(1) and eq(2)

a  

m

​  

+a  

m

′

​  

=a+(m−1)d+l−(m−1)d

a  

m

​  

+a  

m

′

​  

=a+l

Step-by-step explanation:

Answer 2

Answer:

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