Question

the 7th term and 10th term of ap is 12 and 25 find the 12th term
but answer is 101/3
how​

Answer 1

we know that, a n = a+(n-1)d

so, a7 = a + 6d = 12. _ (1)

now, a10 = a+ 9d = 25. _. (2)

now , by using elimination method we can solve this ....

from eq 1 & 2, sub each other...

a+ 6d =12

a+ 9d = 25

-3d= -13

d= 13/3.....

now, put value of d in eq (1) ,

a+ 6× 13/3= 12 = a+ 26= 12 , a = - 14.....

now, a12 = a + 11d = -14+ 11× 13/3 =. -14 + 143/3 =

-42 + 143. =. 101/ 3 .. ...... .......... hence proved,,,,,

3