Let a, b and n be integers with n greater than or equal to 3. We show
that, in the sense of natural density, almost all integers represented
by the binary form ax(n) - by(n) are thus represented essentially uni
quely. By exploiting this conclusion, we derive an asymptotic formula
for the total number of integers represented by such a form. These con
clusions augment earlier work of Hooley concerning binary cubic and qu
artic forms, and generalise or sharpen work of Hooley, Greaves, and Sk
inner and Wooley concerning sums and differences of two nth powers.