Question

Determine the general term of an A.P.whose 7th term is -1 and 16th term is 17.

Answer 1

let a be the first term and d be the common difference
Given, a7 = -1
a 16 =17
now, consider a7 =-1
a+ (7-1)d =-1
a+ 6d =-1.........(1)
consider a16 =17
a+( 16-1) d =7
a+15d =7........(2)
now, subtracting equation (1) from (2) ,we get,
9d=18
d= -2
.: from equation (1), we get,
a= -1 -6d
a=-1 -6× (2)
a=-1 -12
a= -13
now the n^th term of the AP is given by :
an =a + (n-1) d
.: an = - 13+ (n-1) ×2
an =2n -15
.: n^th term of the AP is (2n- 15)

Answer 2

Answer:

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