We could factor the usual way but let's try Dr. Po Shen Loh's "new" method.
First step is to rewrite as a monic,
Now we need two numbers which add to 2/3m and multiply to -5/3m². If they add to 2/3m they average to 1/3m so they're 1/3m-u and 1/3m+u for some u. The product of those two is -5/3m² so we write:
So our equation
factors as
so has roots
The more standard factorization with the same result is
QR. because if BCDE is congruent to OPQR then the sides and angles will be the same also by either sss, sas, asa, or aas depending on how the shape is.