Numbers of Algebra 11
Examples
66 =− 666 = 0
74 .. 4373743 =− 74 .. 4373777. 4343 = 0
- Multiplicative Inverse Property. For every nonzero real
number a, there is a real number called its multiplicative
inverse, denoted a−^1 or^1
a
, such that
aa a
a
a−^1 ==aa⋅
1
1 and a−^1 ⋅ ==⋅
a^11
a
a.
This property guarantees that every real
number, except zero, has a multiplicative
inverse (its reciprocal) whose product with
the number is 1.
- Distributive Property. a(b + c) = a · b + a · c and (b + c) a = b · a + c · a.
This property says that when you have a number times a sum (or a sum
times a number), you can either add fi rst and then multiply, or multiply fi rst
and then add. Either way, the fi nal answer is the same.
Examples
(^3) () (^105) can be computed two ways:
add fi rst to obtain 3 () 105 = 313 545 or
multiply fi rst to obtain 3(10 + 5) = 311030 ⋅ 535 0115545
Either way, the answer is 45.
1
4
3
4
⎛ + 8
⎝
⎛⎛⎛⎛
⎝⎝
⎛⎛⎛⎛ ⎞
⎠
⎞⎞⎞
⎠⎠
⎞⎞⎞⎞ can be computed two ways:
add fi rst to obtain^1
4
3
4
⎛ + 8188
⎝
⎛⎛⎛⎛
⎝⎝
⎛⎛⎛⎛ ⎞
⎠
⎞⎞⎞⎞
⎠⎠
⎞⎞⎞⎞ 1 ⋅ or
multiply fi rst to obtain
1
4
3
4
⎝⎝⎛⎛⎛⎝⎛⎛⎛⎛⎛⎛ + ⎠⎞⎞⎞⎞⎞⎠⎠⎞⎞⎞⎞^8 =
1
4
8
3
4
⋅+ ⋅=+= 8268
Either way, the answer is 8.
Problem State the fi eld property that is illustrated in each of the
following.
a. 0 11252525 = 11. 25
b. ())∈ real numbers
Notice that when you add the additive
inverse to a number, you get the additive
identity as an answer, and when you
multiply a number by its multiplicative
inverse, you get the multiplicative identity
as an answer.
The distributive property is the only fi eld
property that involves both addition and
multiplication at the same time. Another
way to express the distributive property is
to say that multiplication distributes over
addition.
The symbol ∈ is read “is an
element of.”