Question

The 15th term from the last term toward the first term of the A.P:3,7,11,.....123 is

Answer 1

a = 123
d = 3-7
   = -4
so A₁₅ = a +14d
          = 123 + 14 x -4
           = 123 - 56
          = 67

Answer 2

Answer:

In a Given A.P ;

a = 3

d = 7-3 = 4

On the contrary let 144 be the nth term of A.P

Tn = 144

n = ?

Tn = a+(n-1)d

144 = 3+(n-1)4

n-1 = 141/4

n = 35.25+1

n = 36.25

As the value of n is a decimal or number, hence 144 is not the term of given A.P