Question

find the 20th term of AP 7,3,-1,-5.....? please show the solution step by step

Answer 1

Here in this question

a = 7

d = a2 - a1 = 3 - 7 = - 4

an = a + ( n - 1 ) d

a20 = 7 + ( 20 - 1 ) - 4

a20 = 7 + ( 19 × - 4 )

a20 = 7 - 76

a20 = - 69

so the 20th term of this A.P is - 69

Hope it helps you buddy :-)

Answer 2

Given,

A.P. = 7,3,-1,-5,---

To find,

The 20th term of the AP.

Solution,

The 20th term of the AP will be -69.

We can easily solve this problem by following thw given steps.

According to the question,

A.P. = 7,3,-1,-5,---

We know that in an AP the difference between the two consecutive terms is the same which is common difference. The common difference is denoted by the letter, d.

The first term (a) = 7

Common difference (d) = second term - first term

d = 3-7

d = -4

The nth term of an AP is given by the following formula:

an = a+(n-1)d where n is the number of the term

a20 = 7+(20-1)-4

a20 = 7+(19)-4

a20 = 7-76

a20 = -69

Hence, the 20th term of the AP is -69.