Expanding this by the binomial theorem (see p. 141), we get
|
.
|
So, neglecting the small quantities of higher orders of smallness, we have:
.
Subtracting the original
, we find
,
.
And this is still in accordance with the rule inferred above.
Case of a fractional power.
Let
. Then, as before,
terms with higher powers of
.
Subtracting the original
, and neglecting higher powers we have left:
,
and
. Agreeing with the general rule.