Question

4.
The sum of the 5th and 9th terms of an A.P is 26 and the sum of its 7th and
11th terms is 42. Find the first three terms of the A.P.
Ans:-11,-7,-3
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Answer 1

Go through the attachment for solution

Answer 2

Answer:

-11,-7,-3

Step-by-step explanation:

a5=a+4d

a9=a+8d

sum of a5 and a9=a+4d+a+8d

                       26 =2a+12d

         dividing it by 2

                        13=a+6d-equation(1)

a7=a+6d

a11=a+10d

sum of a7 and a11=a+6d+a+10d

                         42=2a+16d

             dividing it by 2

                          21=a+8d-equation(2)

from 1 and 2

                      a+6d=13

                      a+8d=21

                         -2d=-8

                             d=4

   a+6(4)=13

   a=13-24=-11

AP=a,a+d,a+2d

AP=-11,-7,-3