Kleene positive closure - help in proofing this claim I just started a course called 'Automata and Formal Languages'. 
I'm having difficulty in proofing\disproofing this equality. 

$ (L_{1} \circ L_{2})^{+} = L_{1}^{+} \circ L_{2}^{+}
 $

Where:

$ L_{1} $, $L_{2}$ are Languages.

$\circ$ is the concatenation operation between two languages. 

$+$ is the Kleene plus closure defined by $\bigcup  _{i = 1}^{\infty }L^{i} $

I tried finding a counter example and also tried to formally proof but had no luck.
Can someone please point me in the correct direction?
Let's use $A$ for $L_1$ and $B$ for $L_2$.
If you unpack both sides, you get
$$
(AB)^+ = AB + ABAB + ABABAB + \cdots \\
A^+B^+ = AB + AAB + ABB + AABB + \cdots
$$
Perhaps this can give you some ideas.