Question

if sum of3rd and 8th term of ap is 7 and sumof 7th and 14th is -3 find 10 term

Answer 1

a+2d+a+7d=7
This can be written as 2a+9d=7_(i)
a+6d+a+13d=-3
This can be written as 2a+19d=7_(ii)
Now,using (i) and (ii)
2a+9d=7
2a+19d=-3 (we will subtract)
- - +
This will give -10d=10
Or d= 10/-10
Therefore d = -1
Now putting the value of d in eq I
2a+9(-1)=7
=> 2a-9=7
=> 2a=16
=> a=8
So ap= 8,7,6,5,4,3,2,1....
Now 10the term= a+9d
=> 8+9(-1)
=> 8-9=-1
Therefore tenth term is -1 ans_