Question

Which summation formula represents the series below?

Answer 1

we are given

`1+2+6+24`

we can rewrite it as

`1+2*1+3*2*1+4*3*2*1`

so, total number of terms is 4

now, we can find nth term

`a_n=n!`

we can write it in sigma form

`\sum _(n=1)^4\:n!`

we can also write it as

`\sum _(n=2)^5\:(n-1)!`

so, option-A.........Answer