Question

20th term of the list of numbers 5,1,-3,-7 is

Answer 1

Solution :-

The given sequence of numbers is an arithmetic sequence. It is a progression of numbers in which common difference between two consecutive terms is always concept.

nth term of an arithmetic sequence is given by

• an = a + ( n - 1 ) d

Here,

• an = nth term
• a = First term
• d = Common difference
• n = Number of terms

In the given sequence,

• a = 5
• d = 1 - 5 = -4
• n = 20

We have to find value of an.

⇒ an = a + ( n - 1 ) d

⇒ a20 = 5 + ( 20 - 1 ) ( - 4 )

⇒ a20 = 5 + ( 19 ) ( -4 )

⇒ a20 = 5 - 76

⇒ a20 = -71

Hence the required 20th term is -71.