If 2s = a+b+c then the value of [s(s-a)]/3 + [s(s-b)(s-c)]/3 is
a)ab/3
b)bc/3
c)ca/3
d)abc/3
e)a+b+c/3
a)ab/3
b)bc/3
c)ca/3
d)abc/3
e)a+b+c/3
It's easiest to pick numbers.
a = 2, b = 3, c = 7
which makes s = 6 and our target 6*4/3 + 6*3*-1/3, or 2.
Plugging into the answers, we find that only A works, so we're done.
EDIT: See my response below. After trying to make a second post with an algebraic explanation, I discovered that none of the answers are correct.
