Write the First Five Terms of the Following Sequences Whose Nth Terms Are: An = (−1)N 2n - Mathematics

Write the first five terms of the following sequences whose nth terms are:

an = (−1)n 2n

Solution

an = (−1)n 2n

Here, the nth term is given by the above expression. So, to find the first term we use n = 1 we get

a_1 = (-1)^1.2^(1)

= (-1).2

= -2

Similarly, we find the other four terms,

Second term (n = 2)

a_2 = (-1)^2.2^2

= 1.4

= 4

Third term (n = 3)

a_3 = (-1)^3 . 2^3

= (-1).8

= -8

Fourth term (n = 4)

a_4 = (-1)^4 . 2^4

= 1.16

= 16

Fifith term (n = 5)

a_3 = (-1)^5 . (2)^5

= (-1). 32

= -32

Therefore, the first five terms of the given A.P are a_1 = -2, a_2 = 4, a_3 = -8, a_4 = 16, a_5 = -32

Concept: nth Term of an AP
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RD Sharma Class 10 Maths
Chapter 5 Arithmetic Progression
Exercise 5.1 | Q 1.5 | Page 5