Out of three expressions , and , for some integer all three are defined, two take the same integer value, and the remaining one takes a different integer value. For which pairs of integers is this possible?
(Bohdan Rublyov)
Out of three expressions , and , for some integer all three are defined, two take the same integer value, and the remaining one takes a different integer value. For which pairs of integers is this possible?
(Bohdan Rublyov)
Obviously, , for , since otherwise, the first fraction will not be an integer. If the first two expressions are equal, then we have the equality:
For and possible range of values, the given equality is satisfied only by pairs , . The third expression will obviously take a non-zero, but non-integer value, since for .
If the first and third expressions are equal, we have the equality:
The possible pairs of are (2, 1) and (-2, -1). Here, the second expression in the first case will take on a value 3, hence, different from the other two. In the second case, it is not defined and, therefore, not possible.
If the second and third expressions are equal, we have the equality:
and does not satisfy the conditions.
is not integer, so does not satisfy the conditions.
does not lie in the allowed range of values.
and satisfies the conditions.