374 
ON THE THEORY OF ELIMINATION. 
[59 
which may be represented as before by 
Thus, for instance, selecting the firsr, second, and sixth lines of O' to form the 
determinant Q\ we have (/ = a" (a'b" — a"b') ; and then Q must be formed from the 
third, fourth, fifth, seventh, &c. ... eighteenth lines of 12. (It is obvious that if Q' had 
been formed from the first, second, and third lines of i2', we should have had Q' = 0; 
the corresponding value of Q would also have vanished, and an illusory result be 
obtained; and similarly for several other combinations of lines.)