find the remainder when-

http://latex.codecogs.com/gif.latex?...10}(n^{2}+n)n!

is divided by 10.

No idea. (Thinking)

i just know the sum of n.n!=(n+1)!-1

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- May 5th 2009, 07:15 PMadhyetafind the remainder
find the remainder when-

http://latex.codecogs.com/gif.latex?...10}(n^{2}+n)n!

is divided by 10.

No idea. (Thinking)

i just know the sum of n.n!=(n+1)!-1 - May 5th 2009, 07:25 PMTheEmptySet
Notice for $\displaystyle n \ge 5 $ each term is divisable by 10 so they have a remainder of zero(why)

Now we only need to worry about the first 4 terms

We also don't need to worry about the 4 term (why)

so we get $\displaystyle (2)1+(6)2+12(6)=86$ so the remainder is 6 - May 5th 2009, 07:43 PMadhyeta