Question

Sn = 3n^{2} + 6n ,find 10th term

Answer 1

Answer:

Sn = 3n²+ 6n

S1 = a1 = 3(1)² + 6(1) = 9

then first term is 9

S2 = a1+a2 = 3(2)² +6(2)

S2 = 12 + 12 = 24

from here a2 = 24 - a1 = 24 - 9 = 15

a2 = 15

S3 = S2 + a3 = 3(3)² + 6(3)

S3 = 27 + 18

from here a3 = 27 + 18 - S2 = 27 + 18 - 24 = 21

a3 = 21

so d = a2 - a1 = 15 - 9 = 6

so the common difference is 6

10th term

a10 = a+(10-1)d

a10 = 9 + 9(6)

a10 = 63

thus 10th term is 63

Answer 2

Answer:

Answer is 63

Step-by-step explanation:

a2 is 15

a1 is 9

D is 6

an=a+(n-1)d

an=9+(9)6

an=9+54

an=63