Mathematical derivation

#1

How below equation get transferred to second equation

1 + n/n-1 + 1/(n-2) + 1/(n-3) + … + n

To
n ( 1 + 1/2 + 1/3 + . …+ 1/n)

#2

Hello @nirmal1067
Just reversing the series.
n/n + n/n-1 + n/n-2…+n
is same as n(1/n + 1/n-1 + 1/n-2 …1)
is same as n(1 + 1/2 + 1/3 + 1/4 …)
We have taken infine series…