#Where am I mistaking?

12 messages · Page 1 of 1 (latest)

strong basalt
#

We know the formula for cubic series sum is [{n(n+1)}/2]^2. In the problem we use that formula to show that the other side is divisible by n^2. But then, shouldnt that be applicable also for even? but that doesnt happen. So, where am I making the mistake?

image.png
livid tideBOT
strong basalt
#

For example, take n=2. then it comes 4|9. but that isnt true

undone osprey
#

alright

#

so if you take the n and put it instead of 1 it can be -1m

strong basalt
#

wait wait

#

i just realized

#

if u take n to be an even number

#

the coefficient of n on the numerator gets divided due to the 2 under the fraction

#

and therefore

#

it isnt divisible anymore

#

by n squared