00:02
So in this problem we need to prove that ab comma c is equal to a b c plus a b bracket b.
00:26
So we need to prove this equation.
00:31
Now we know that the commutator of two contenders.
00:44
Entities, a and b is defined as a, comma, b is equal to ab minus b.
01:10
This implies that ab is equal to a b, c, is equal to a, b, c minus c, a, b.
01:23
So it means that we can add ac b negative ac b to the previous equation and it will give us that ab comma c is equal to ab c negative c ab positive acab positive ac b negative a, c, b.
02:03
Now what are we going to do over here? we can, from this equation we can write that a parenthesis b -c minus c -b plus ac minus c -a parenthesis b and from this equation we can conclude that a bracket b -c plus a, c, bracket, b.
02:42
And then we can conclude that a, b, c is equal to a, b, c, plus a, c, b...