Substitution

Definition

Substitution is the process of replacing one variable or expression with another, often to simplify an algebraic expression or equation. This technique is widely used in various mathematical contexts, including using the language of algebra, factoring trinomials, and solving equations in quadratic form.

5 Must Know Facts For Your Next Test

1. Substitution allows you to simplify complex expressions by replacing parts of the expression with a single variable or value.
2. In the context of using the language of algebra, substitution is used to evaluate expressions by replacing variables with given values.
3. When factoring trinomials, substitution can be used to identify the factors of the expression by replacing the variable with a value that makes the expression easier to factor.
4. Solving equations in quadratic form often involves substituting expressions to isolate the variable of interest and find the solution.
5. Substitution is a fundamental algebraic technique that enables you to manipulate and transform expressions and equations to arrive at the desired result.

Review Questions

• Explain how substitution is used in the context of evaluating algebraic expressions.
  • When evaluating an algebraic expression, substitution is used to replace the variables with specific values. This allows you to simplify the expression and calculate its numerical value. For example, if you have the expression $2x + 3$ and you are told that $x = 5$, you can substitute $x$ with 5 to get $2(5) + 3 = 13$, which is the evaluated expression.
• Describe how substitution can be used to factor trinomials.
  • Factoring trinomials often involves identifying values for the variables that make the expression easier to factor. Substitution can be used to replace the variable with a value that reveals the factors. For instance, if you have the trinomial $x^2 + 5x + 6$, you can substitute $x$ with a value like 2 or -3 to get $2^2 + 5(2) + 6 = 4 + 10 + 6 = 20$, which can be factored as $4 \cdot 5$. This substitution technique helps you determine the factors of the original trinomial.
• Analyze how substitution is employed when solving equations in quadratic form.
  • When solving equations in quadratic form, such as $ax^2 + bx + c = 0$, substitution is used to isolate the variable of interest. This may involve replacing the quadratic expression with a simpler variable, like $y = ax^2 + bx + c$, and then solving the resulting linear equation for $y$. Alternatively, the quadratic formula, which involves substituting the coefficients $a$, $b$, and $c$ into a predetermined expression, can be used to find the solutions to the equation. Substitution is a crucial step in the process of solving equations in quadratic form.

Related terms

Variable:

A symbol, usually a letter, that represents an unknown or changeable quantity in an algebraic expression.

Expression: A mathematical phrase that combines variables, numbers, and operations to represent a value.

Equation: A mathematical statement that shows two expressions are equal, often used to solve for an unknown value.