Basic Algebra/Introduction to Basic Algebra Ideas/Variables and Expressions
A variable is a letter or symbol that takes place of a number in Algebra. Common symbols used are , , , and . The letters x and y are commonly used, but remember that any other symbols would work just as well.
Variables are used in algebra as placeholders for unknown numbers. If you see "3 + x", don't panic! All this means is that we are adding a number who's value we don't yet know.
Some examples of variables in use:
- -- three times of .
- -- five minus
- or -- 2 divided by
A term is a number or a variable or a cluster of numbers and variables multiplied and or divided separated by addition and subtraction.
Examples of terms:
- The terms are 3 and 5.
- The term is , 6 over is one term, because the operation is division.
- The terms are 6 and 5, 6 and 5 are separate terms because they are separated by a addition or subtraction.
An operation is a thing you do to numbers, like add, subtract, multiply, or divide. You use signs like +, –, *, or / for operations.
An expression is two or more terms, with operations between all terms.
Examples of expressions:
To evaluate an expression, you do the operations to the terms of an expression.
Examples of evaluating expressions:
- evaluates to 7.
- evaluates to 6.
- evaluates to 17.
To evaluate an expression with variables, you substitute (put a thing in the place of an other thing) numbers for the variables.
Examples of substituting: (Substitute 3 for x in these examples.)
- is .
- is .
- is .
Evaluate when is 2.
Substitute 2 for to get .
Evaluate to get the answer 10.
Evaluate when is 9 and is 4.
Substitute 9 for and substitute 4 for is to get .
Evaluate to get the answer 7.
remember order of operations