To find nth term of the arithmetic sequence, we use the formula
an = a1 + (n – 1)d
Here a1 is the first term, n represents the position of the term and d represents the common difference.
a) Find
the common difference of each arithmetic sequence.
b) Write the nth term of each sequence for the given value of n.
Problem 1 :
3, 6, 9, 12, …, n = 8
Solution :
a) Common difference :
a1 = 3, a2 = 6, a3 = 9
d = a2 – a1 = 6 - 3 = 3
So, the common difference is 3.
b) Finding the 8th term :
an = a1 + (n – 1)d
a8 = 3 + (8 – 1)3
= 3 + 7(3)
= 3 + 21
a8 = 24
So, the 8th term of the sequence is a8 = 24.
Problem 2 :
2, 7, 12, 17, …, n = 12
Solution :
a) Common difference :
a1 = 2, a2 = 7, a3 = 12
d = a2 – a1 = 7 - 2 = 5
So, the common difference is 5.
b) nth term of sequence :
an = a1 + (n – 1)d
Finding 12th term :
a12 = 2 + (12 – 1)5
= 2 + 11(5)
= 2 + 55
a12 = 57
So, the nth term of the sequence is a12 = 57.
Problem 3 :
18, 16, 14, 12, …, n = 10
Solution :
a) Common difference :
a1 = 18, a2 = 16, a3 = 14
d = a2 – a1 = 16 - 18 =
-2
So, the
common difference is -2.
b) 10th term of sequence :
an = a1 + (n – 1)d
a10 = 18 + (10 – 1)(-2)
= 18 + 9(-2)
= 18 - 18
a10 = 0
So, the 10th term of the sequence is a10 = 0.
Problem 4 :
1/2, 1, 3/2, 2, …, n = 7
Solution :
a) Common difference :
a1 = 1/2, a2 = 1, a3 = 3/2
d = a2 – a1 = 1 – 1/2
= (2 – 1)/2
= 1/2
So, the
common difference is 1/2.
b) 7th term of sequence :
an = a1 + (n – 1)d
a7 = 1/2 + (7 – 1)(1/2)
= 1/2 + 6(1/2)
= 1/2 + 6/2
a7 = 7/2
So, the nth term of the sequence is a7 = 7/2.
Problem 5 :
-1, -3, -5, -7, …, n = 10
Solution :
a) Common difference :
a1 = -1, a2 = -3, a3 = -5
d = a2 – a1 = -3 + 1 =
-2
So, the
common difference is -2.
b) 10th term of sequence :
an = a1 + (n – 1)d
a10 = -1 + (10 – 1)(-2)
= -1 + 9(-2)
= -1 - 18
a10 = -19
So, the nth term of the sequence is a10 = -19.
Problem 6 :
2.1, 2.2, 2.3, 2.4, …, n = 20
Solution :
a) Common difference :
a1 = 2.1, a2 = 2.2, a3 = 2.3
d = a2 – a1 = 2.2 – 2.1
= 0.1
So, the
common difference is 0.1.
b) 20th term of sequence :
an = a1 + (n – 1)d
a20 = 2.1 + (20 – 1)(0.1)
= 2.1 + 19(0.1)
= 2.1 + 1.9
a20 = 4
So, the nth term of the sequence is a20 = 4.
May 21, 24 08:51 PM
May 21, 24 08:51 AM
May 20, 24 10:45 PM