420999 420999
  • 02-05-2021
  • Mathematics
contestada

Suppose {an) is an arithmetic sequence with a16=12 and a7=30. Find a9.

Respuesta :

abidemiokin
abidemiokin abidemiokin
  • 07-05-2021

Answer:

a9 = 26

Step-by-step explanation:

nth term of an arithmetic sequence an = a + (n-1)d

a16 = a+15d = 12.... 1

a7 = a+6d = 30.....2

Subtract

15d - 6d = 12 - 30

9d = -18

d =-18/9

d = -2

Substitute d = -2 into 1

a + 15d = 12

a+15(-2) = 12

a - 30 = 12

a = 12 + 30

a = 42

Get a9;

a9 = a+8d

a9 = 42+8(-2)

a9 = 42 - 16

a9 = 26

hence the 9th term of the sequence is 26

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