Question

The sum of the 1st and 17th term of an arthemetic sequnce is 40 the sum of its 1st and 18th term is 43 what is its common difference

Answer 1

 let  first term= $x_{1}$

 then the 17th term =$x_{17}$

1.then sum of first term and 17th term =$x_{1} +x_{17} =40$

2.then sum of first term and 18th term=$x_{1} +x_{18} =43$

then the difference of 2 equation and 1 equation

                $x_{1} +x_{18} =43$ - $x_{1} +x_{17} =40$ = $x_{1}$=3

          first term = 3

       ∴ d,common difference = $\frac{x_{17}-x_{1}}{7-1}$

Answer 2

Answer:

let  first term= x_{1}x1

 then the 17th term =x_{17}x17

1.then sum of first term and 17th term =x_{1} +x_{17} =40x1+x17=40

2.then sum of first term and 18th term=x_{1} +x_{18} =43x1+x18=43

then the difference of 2 equation and 1 equation

                x_{1} +x_{18} =43x1+x18=43 - x_{1} +x_{17} =40x1+x17=40 = x_{1}x1 =3

          first term = 3

       ∴ d,common difference = \frac{x_{17}-x_{1}}{7-1}7−1x17−x1