2P2+3P2+4P2+5P2+....+24P2+25P2

Question

anonymous · Answer

$$(\frac{n(n+1)}{2}-1)p2$$

parthkohli · Answer

$$\large \sum_{i = 2}^{25}P(i,2)$$This is a good question.

eyust707 · Answer

n = 25

parthkohli · Answer

Careful, P means "permutations".

anonymous · Answer

Ya never can tell.. sometimes these guys just mean squared.... but I bet you're right.

anonymous · Answer

If @ParthKohli is correct... I entered sum(seq( x nPr 2 , x ,2 ,25)) into my TI-84 and got an answer.

hartnn · Answer

m getting 
$$\sum_{2}^{25}n(n-1)$$

anonymous · Answer

$$1\times2+2\times3+...+24\times25$$

hartnn · Answer

or $$\sum_{1}^{24}n(n+1)$$

hartnn · Answer

this can be solved.

anonymous · Answer

@hartnn I got the same answer with your minus version

hartnn · Answer

$$\sum_{1}^{24}n^2+n$$

anonymous · Answer

$$=\frac{24(24+1)(48+1)}{6}+\frac{24.25}{2}$$

hartnn · Answer

yup, thats it ^^

anonymous · Answer

hah, and plus version

hartnn · Answer

4*25*49+12*25=5200
did u get 5200 @EulerGroupie ?

anonymous · Answer

I did a sum of sequences of permutations in my calculator and got 5200

hartnn · Answer

@diazmayendra is not even here to understand this.

anonymous · Answer

@diazmayendra medal'd me and moved on to the next question

hartnn · Answer

okk....

anonymous · Answer

but I like it when people back these things up with more info... that's when I learn on stuff that I am weak on.

parthkohli · Answer

anonymous · Answer

new site added to favorites, thank you @ParthKohli

parthkohli · Answer

@EulerGroupie the Mathematics on that site is advanced :)

anonymous · Answer

i not understand this question and i not understand too your answer