Question

In an AP, the 7th term is 30 and the 10th term is 21. Find the first term, common difference and its n th term.

Answer 1

we can write 7term as

a+6d=7term equation 1

and its 10 term =a+9d equation 2

from equation 1and 2we found that common difference =-3 and its first term will be 48 and its nth term will be 51-3n

Answer 2

7=a+6d

10=a+9d

a+6d=30

a+9d=21

- - -

-3d=9

d=9/-3

d=3

a+6d=30

a+6*3=30

a+18=30

a=30-18

a=12