Question

The first term of 2 AP's are equal & the
ratios of the common difference is 1:2if the 7 th term of first Ap & 21 term of second ap are 23 & 125 respectively find the ap's​

Answer 1

Answer:

Step-by-step explanation:

Let the first term of two AP be a

and common difference be d,2d(where d is an integer)

According too Question

7th term=23

21th term=125

By formula,

                  $a_{n}$=2a+(n-1)d

• case 1                                  case 2

        $a_{7}$=2xa+(7-1)d                      $a_{21}$=2xa+(21-1)2d

        23=2a+6d-(i)                       125=2a+40d-(ii)

  Eliminating i and ii

23=2a+6d

125=2a+40d

-       -      -

-102=-34d

d=3

∴a=2.5

∴ap,

       2.5,5.5,8.5,........

       2.5,8.5,14.5,..........