Question

sum of first n term of an arithmetic sequence 5n^2+2n find the common difference ​

Answer 1

Answer:

common difference = 10

Step-by-step explanation:

Sn = 5n² + 2n

S1 = 5(1²) + 2(1)

= 5 + 2

= 7

S2 = 5(2²) + 2(2)

= 20 + 4

= 24

S3 = 5(3²) + 2(3)

= 45 + 6

= 51

S1 = a1 = 7

S2 = a1 + a2 = 24 ;

7 + a2 = 24

a2 = 24 - 7

a2 = 17

S3 = a1 + a2 + a3 = 51

7 + 17 + a3 = 51

a3 = 51 - 24

a3 = 27

the AP is 7, 17, 27, ........

common difference = d

a2 - a1 = a3 - a2

17 - 7 = 27 - 17

10 = 10

therefore the common difference = d = 10

hope you get your answer