Question

if the sum of the first 7 terms is 49 and that of the first 10 terms is 100 find the AP​

Answer 1

Answer:

a7 =49

i.e., a+6d =49-----eq.1

and a10 = 100

i.e., a+9d = 100-----eq.2

Subtraction by elimination methord

i.e., a+6d=49

a+9d=100

___________

- 3d = - 51

___________

d = -51/-3

d= 17

Putting the value of d in the equation 1

We get,

a + 6(17) = 49

a = - 102 + 49

a = - 53

So,

AP : - 53, - 36, - 19,.......,