Geometric-harmonic mean
From Wikipedia, the free encyclopedia.
In
mathematics, the
geometric-harmonic mean M(
x,
y) of two positive
real numbers x and
y is defined as follows: we first form the
geometric mean of
x and
y and call it
g1, i.e.
g1 is the
square root of
xy. We then form the
harmonic mean of
x and
y and call it
h1, i.e.
h1 is the
reciprocal of the
arithmetic mean of the reciprocals of
x and
y.
Now we can iterate this operation with g1 taking the place of x and h1 taking the place of y. In this way, two sequences (gn) and (hn) are defined:

and

Both of these sequences
converge to the same number, which we call the
geometric-harmonic mean M(
x,
y) of
x and
y.
M(x, y) is a number between the geometric and harmonic mean of x and y; in particular it is between x and y. If r > 0, then M(rx, ry) = r M(x, y).
See also