Math, asked by sunkarisunitha1983, 8 months ago

consider the AP 2, 5,8,11,.....302 show that twice of the middle term of the above AP is equal to the sum of its first and last term​

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Answered by swastika07642
5

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Answered by sanketj
5

For the A.P.

first term, a = 2

common difference, d = 3

last term, A = 302

let the total number of terms be 'n'

An = 302

a + (n - 1)d = 302

2 + (n - 1)(3) = 302

(n - 1)(3) = 300

n - 1 = 100

n = 101

number of terms is odd, hence position of the middle term will be

 \frac{n + 1}{2}  =  \frac{101 + 1}{2}  =  \frac{102}{2}  = 51

hence, middle term–

 a_{51} = a + 50d = 2 + 50 \times 3 = 2 + 150 \\  a_{51}  = 152 \\ 2 a_{51}  = 304 \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \: ... \: (i)

sum of first and last term–

 \:  \:  \:  \:  \:  \: a +  a_{101}  \\  = 2 + 302 \\  = 304 \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \:  \: \:  \:  \:  \:  \:  \:  \:   \:  \:  \:  \:  \:  \:  \: ... \:  (ii)

from (i) and (ii)

2 a_{51} = a +  a_{101}

Hence, for the given A.P, twice the middle term is equal to the sum of the first and the last term.

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