Question

the sum of n terms of ap is 3n+n^2 then find first term and sum of first term​

Answer 1

sum of first n terms = 3n+n^2

first term of the AP (x1) =4

fifth term of the AP (x5)=40

sum of first 5 terms(s5)= 1/2(x1+x5)

=1/2(4+40)

=1/2×44

=22

second term of the AP (x2)=10

third term of the AP(x3)=18

15th term of the AP (x15)=225

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Answer 2

xn= 3n+n²

x1= 3×1+1²

= 4

first term = 4

sum of first term = 4