Question

Find the middle most term of the A.P -11,-7,-3...........,49

Answer 1

-11,-7 , -3 ......,49 is in AP

first term = a = -11

common difference =d = a2- a1= -7-(-11) = -7 +11 = 4

last term = l = 49

a +(n-1)d =49

-11+(n-1)4 =49

(n-1)4 =49+11

(n-1)4 = 60

n-1 = 60/4

n-1 = 15
n= 15 +1 =16
number of terms are in AP is 16

middle terms or 8th and 9th terms

a8 = a+7d = -11+7*4 = -11+28 = 17

a9 = a +8d = -11+8*4 =-11+32 = 21

Answer 2

-11 , -7 , -3 ......... 49

In given ap ,

a = -11

d = -7 - (-11) = -7 + 11 = 4

An = 49

An = a + ( n - 1 ) d

49 = -11 + ( n - 1 ) 4

49 + 11 = ( n - 1 ) 4

60 / 4 = ( n - 1 )

n - 1 = 15

n = 15 + 1

n = 16

So the middle most term is 8 th or 9 th term