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CHAPTER XI.

ON TAE OPERATIONS OF ADDITION AND SUBTRACTION IN

SYMBOLICAL ALGEBRA.

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a

543. The symbols in Arithmetical Algebra represent num- Distinction

between bers, whether abstract or concrete, whole or fractional, and the

Arithmetic operations to which they are subject are assumed to be identical and Arith

metical in meaning and extent with the operations of the same name Algebra in common Arithmetic: the only distinction between the two sciences consisting in the substitution of general symbols for digital numbers.

Thus, if a be added to b, as in the expression a+b, it is assumed that a and b are either abstract numbers or concrete numbers of the same kind: if b be subtracted from a, as in the expression a b, it is assumed that a is greater than b, which implies likewise that they are numbers of the same kind: if a be multiplied by b, as in the expression ab (Art. 34), or if a be divided by b, as in the expression g (Art. 71), it is assumed that 6 is an abstract number. In all these cases, the operation required to be performed, whether it be addition or subtraction, multiplication or division, is clearly defined and understood, and the result which is obtained, is a necessary consequence of the definition: the same observation applies to all the results of Arithmetical Algebra.

544. But the symbols, which are thus employed, do not The asconvey, either to the eye or to the mind, in the same manner as

sumption

of the undigital numbers and geometrical lines, the limitations of value to limited

values of which they are subject in Arithmetical Algebra: for they are the symbols equally competent to represent quantities of all kinds, and of all employed

involves the relations of magnitude. But if we venture to ascribe to them necessary a perfect generality of value, (upon which a conventional limi- of the indetation was imposed in Arithmetical Algebra), it will be found pendent use

of the signs to involve, as an immediate and necessary consequence, the + and VOL. II.

A

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