The Most Valuable and Important
. . .
Shown and Explained
Background - why plus-minus signs are used. . .
Symbols are a concise way of giving lengthy instructions related to
numbers and logic.
Math Symbols are an invention, not a discovery. They are a
communication tool. Symbols are used to eliminate
the need to write long, plain language instructions to describe
calculations and other processes.
The most valuable, most frequently used Symbols in mathematics . . .
The most important, most frequently used Miscellaneous Symbols
are listed below.
Math Symbol for "Plus-Minus" -
symbol means that the number (to the right of the symbol) is two numbers: a positive number AND a negative number.
8 stands for two numbers:
+8 and -8
symbol is commonly used:
In mathematical expressions and equations.
To quantify the margin or error (precision) of a computation or measurement.
, use in Mathematical Expressions and Equations
The use of the plus-minus symbol is a short hand way of showing that the square root of 256 has two answers:
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:
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:
, used to show "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:
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: