Math Symbols are
a communication
tool. Symbols are an
invention which is
used to eliminate
the need to write
long, plain language
instructions to
describe
calculations and
other processes.

The
symbol
means
that the
number (to
the right
of the
symbol) is
really
two
numbers:
a positive
number
*AND*
a negative
number.

For Example,
8
stands for
two
numbers:

+8
and
-8

The
symbol is
commonly
used:

(1) In
mathematical
expressions and
equations.

(2) To quantify
the margin or
error
(precision) of
a computation
or
measurement.

Example 1:
, use
in
Mathematical
Expressions
and
Equations

Square
Root:

The use of the
plus-minus
symbol is a
short hand way
of showing that
the square root
of 256 has two
answers:

Absolute
Value:

This absolute
value equation
can be
rewritten using
the plus-minus
symbol:

The use of the
plus-minus
symbol clearly
shows that two
equations must
be solved to
determine the
values of x
which satisfy
the original
equation. These
equations
are:

Quadratic
Equation:

The use of the
plus-minus
symbol shows
that two
equations must
be solved to
determine which
values of x
satisfy the
quadratic
equation. These
equations
are:

(1) Using the
"plus"
sign:

(2) Using the
"minus"
sign:

Example 2:
, use
in
"Precision"
or
"Margin
or
Error"

Margin of
Error:

A local poll
taken May 1-4
of 1200
registered
voters showed
Candidate A
would beat
Candidate B if
the election
were held now,
60 to 30
percent, with
seven percent
undecided. This
poll has a
margin of error
of plus or
minus four
percentage
points.

Candidate A
should receive
between 56% and
64% of the vote
if the election
were held
today.

This could be
written:

Candidate A

Likely Vote

Engineering
Tolerance:

A round pin is
being
manufactured to
fit into a
round hole,
which is 20 mm
in diameter.
The round pin
might have a
manufacturing
specification
of 19.95 mm to
19.99 mm in
diameter.

Using the
plus-minus
sign, this
could be
written:

Diameter of

Round Pin

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