468
ON THE BINOMIAL THEOREM,
[533
For
a, /3
a, b, c, d, e)i
a,
a,
a
a
a,
a,
/3
a
a,
a,
/3,
/3
a
P,
/3,
/3
a
/3,
f3,
A
/3
b
viz. the expression is
(a — a) (a - b) (a — c) (a — d) ... + (/3 — b) (/3 - c) (/3 - d) (/3 - e).
Finally for
( a 7 . | write a, a, a, a, a \ a, b, c, d, e\
\a, b, c, d, el 5
viz. the expression is
(a — a) (a — b) (a — c) (a — d) (a — e),
which explains the law of the formation of the several coefficients. It is to be observed
that in forming the development of any symbol, for instance f a> f’ ^ 1 > the first
\a, o, c, ct, ej 3
column contains the homogeneous products, 3 together, of a, /3, 7; the second column
the combinations (that is, combinations without repetitions) 3 together of a, b, c, d, e :
the top line is a, a, a | a, b, c and to form the subsequent lines we must for any
advance a into /3, &c. of a greek letter make the like advance a into b, b into c, or
c into d, of the corresponding latin letter.
Two particular cases of the theorem may be noticed : if the latin letters all vanish,
we have, for example,
h 5 = (h — a) (h — /3) (h — 7) (h — 8) (h — e).
+ (h — a) (h — /3) (h — 7) (h - 8)
+ (h — a)(h — P) (h - 7)
+ (h - a) (h - p)
+ (h — a)
+ 1
• H 1 (a, /3, 7, S, e)
• /3, 7, 8)
• H z (a, /3, 7)
.# 4 (a, /3)
• H 5 (a),
where the symbols H denote the sum of the homogeneous products of the annexed
letters, taken together according to the suffix number : the last coefficient H 5 (a) is of
course = a 5 . And if the greek letters all vanish, then we have in like manner
(.h — a) (h — b) (h — c) (h — d) (h — e) = It 5
— /i 4 Ci (a, b, c, d, e)
+ h 3 C 2 (a, b, c, d, e)
— h?C 3 (a, b, c, d, e)
+ hC 4 (a, b, c, d, e)
— C 5 (a, b, c, d, e),