Why is $1-\frac{1}{(n+1)}+\frac{1}{(n+1)(n+2)}=1-\frac{(n+2)-1}{(n+1)(n+2)}?$

This is a step during a mathematical induction inside a textbook example I don't get

Also, if anyone has some good online resources to practice this sort of stuff, I'd be eternally grateful!

This is a step during a mathematical induction inside a textbook example I don't get

Also, if anyone has some good online resources to practice this sort of stuff, I'd be eternally grateful!