Basic Algebra/Introduction to Basic Algebra Ideas/Variables and Expressions

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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 .

Example Problems[edit]

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.

Practice Games[edit]

Practice Problems[edit]

Evaluate each expression if = 1, = 2, = 3, and = 5. remember order of operations

Evaluate each expression if = 4, = 2, and = 3.

More harder questions:

Evaluate each expression if = 5, = 8, and = 9.

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Variables and Expressions
Order of Operations Working With Negative Numbers