When proving an identity it is usually best to start with the more
complicated expression and simplify it so this time start with the
expression on the right hand side $(k+1)! - k!$. The algebra is
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities
can be found here.