IN A recent issue of the Mathematics Teacher , Nicolai (1974) detailed several “discoveries” in linear algebra that were made by him and one of his classes. A look at their ideas yielded several discoveries showing that the relationships described by Nicolai are special cases of more general, interesting situations.
As Nicolai proved, {(-1,2)} is the solution set of all pairs of linear equations where the coefficients and right – hand members of the equations are terms of any arithmetic sequence; that is,
Where d is the common non zero difference in the arithmetic sequence. But {(-1,2)} is also the solution set of the following system:
3x + 6y = 9
7x + 10y = 13
It is easily seen that the coefficients and right – hand members of the two equations are not the terms of a single arithmetic sequence and thus do not satisfy the conditions specified in Nicolai’s case. Notice, however, that the coefficients and right – hand member of each separate equation are members of an arithmetic sequence and that the common difference in both arithmetic sequences is the same, in this case 3. This observation led to an attempt to prove that