Question

the sum of 4 and 8 terms of an ap is 24 and the sum of 6 and 10 term is 34 find the first term and common differenc​

Answer 1

Answer:

d=2.5 and a=-0.5

Step-by-step explanation:

Given that the sum of 4 and 8 terms of an ap is 24

⇒a+3d+a+7d=24

⇒2a+10d=24

⇒a+5d=12      → 1st equation

given that the sum of 6 and 10 terms of ap is 34

⇒a+5d+a+9d=34

⇒2a+14d=34

⇒a+7d=17  →2nd equation

solving 1st and 2nd equations

           a+5d=12

          a+7d=17

        _[-]_[-]___[-]________

        -2d=-5

        2d=5

        d=5/2

       d=2.5

      ⇒a=   substituting d in any one of the equation

        a+5d=12

        a+5[2.5]=12

        a=12-12.5

       ∴a=-0.5