Question

If the 5 th and 21 st term of an AP are 14 and -14 respectively than which term of the AP is 0

Answer 1

Answer:

13nth term of AP = 0

Step-by-step explanation:

5th term of AP = a+4d

21st term of AP= a+20d

given,

a+4d= 14..........(1)

a+20d= -14.......(2). from these eqns.

=> 16d= -28

=> d= -28/16= -7/4

=> a+ 4×-7/4= 14

=> a = 21

let nth term is 0

=> a+(n-1)d =21+(n-1)(-7/4)= 0

=> (n-1)(-7/4) = -21

=> n-1 = -21× -4/7= 12

=> n= 13

thus, 11nth term of AP is 0.

short method:-

adding eqns (1) and (2)

2a+24d=0

=> a+12d = 0 => a+ (13-1)d=0

= 13nth term =0

Answer 2

Step-by-step explanation:

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