No. of permutation of n- different things taken

at a time when

perticular things is to be always included in each arrangement is

answer Given is

My solution:: Here

perticular objects are always included So we arrange

objects out of total

objects

Which can be done in

Now arrange

perticular objects which can be done in

ways

Now arrange

objects Simultaneously which can be done by

ways.

My Doubt is why answer is given only

Thanks