Subtraction Rule One
Algebra Help: Section 2.8
Change the sign of the subtrahend.
5. OPERATION
From15a10a5a0 Take5a5a5a5a___________________ Difference10a5a0 -5a
ANALYSIS - Since
the minuends decrease by 5a toward
the right, and the
subtrahends are all equal, the remainders must decrease by 5a,
and the last remainder is therefore -5a.
We cannot, numerically, take a greater quantity
from a less, nor any quantity from zero, for no quantity
can be less than nothing. Hence, in the last two
examples, the answer -5a, is not 5a less than nothing,
but 5a applied in the opposite direction to +5a.
To subtract a quantity algebraically,
is to change the direction in which it is applied.
Thus, we see that by a change of sign, we can find the algebraic difference between any two quantities whatever.
From these examples and illustrations we derive the following.
- Change the sign of the subtrahend, or conceive it to be changed, and unite the terms as in addition.
Pages 34-35
Pages 34-35
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By Horation N Robinison, LL. D. Ivison, Blakeman & Company, Publishers, New York and Chicago.
