Question

If the 7th term of a sequence is 33 and the 10th term is 21, find the common difference d?

Answer 1

`d=-4`

Explanation:

Given conditions are
`a7=33`
`a10=21`
we have to find 'd'
we have arithmetic sequence relation
`an=a+(n-1)d`
from given data we can write
`a7=a+(7-1)d`
`33=a+6d`........ (1)
and
`a10=a+(10-1)d`
`21=a+9d`........(2)
Subtract eq (2) from (1) we have now
`-12=3d`
Therefore
`d=-4`