Commuting Operators

Homework Statement

It is known that ##M_1,M_2, M_3## commute with each other but I don't see how the second line is achieved even though it says that it's using that ##M_1## and ##M_2## commute?

Related Introductory Physics Homework Help News on Phys.org
TSny
Homework Helper
Gold Member
Note M2(1+M1) = M2 + M2M1

How can you rewrite the right hand side using the fact that M1 and M2 commute?

Note M2(1+M1) = M2 + M2M1

How can you rewrite the right hand side using the fact that M1 and M2 commute?
##M_2 + M_1M_2##

TSny
Homework Helper
Gold Member
##M_2 + M_1M_2##
OK. Can you see something you can do with this expression that will help?

OK. Can you see something you can do with this expression that will help?
##(1 +M_1)M_2## ?

TSny
Homework Helper
Gold Member
Yes.