Question

the sum of the first n term of an AP is 5n2-3n . find the AP and hence find 12th term​

Answer 1

Answer:

a1 = 5n^2 - 3n

= 5 - 3

= 2

s2 = 5(2)^2 - 3(2)

= 20 - 6

= 14

a2 = s2 - a1

= 14 - 2

= 12

s3 = 5(3)^2 - 3(3)

= 45 - 9

= 36

a3 = s3 - s2

= 36 - 14

= 22

AP = 2, 12, 22

a = 2

d = 10

a12 = 2 + 110

= 112