Question

Pop quiz for y'all minds out there!\[\large \sum_{i = 2}^{25}P(i,2)\]

Answer 1

Ssh. ;)

Answer 2

P=permutation

Answer 3

I'm not familiar with this notation, what is \(P(i, 2)\) representing?

Answer 4

oh.

Answer 5

i won't just clearing what's P

Answer 6

OK, thank you!

Answer 7

\[=\sum{\frac{i!}{(i-2)!}}=\sum{i(i-1)}=\sum{(i^2-i)}\] for i=1 to 25.
\[\sum{i^2}=\frac{n(n+1)(2n+1)}{6}\]
For n=25 this is 5525.
\[\sum{i}=\frac{n(n+1)}{2}\]
For n=25 this is 325.
So \(\sum{(i^2-i)}=5525-325=5200\)
Did I go wrong somewhere?

Answer 8

wow!

Answer 9

Very good, very good!

Answer 10

in 1st shot!

Answer 11

Yay, thanks :)