2-1 Introduction to Algebra
Key Concepts of Algebra
Algebra is a branch of mathematics that uses symbols and letters to represent numbers and quantities in equations and formulas. It is a powerful tool for solving problems and understanding relationships between different quantities.
1. Variables and Constants
In algebra, variables are symbols (usually letters) that represent unknown values. Constants are fixed values that do not change. For example, in the equation \( y = 2x + 3 \), \( x \) is a variable, and 2 and 3 are constants.
Example:
In the expression \( 5x + 7 \), \( x \) is the variable, and 5 and 7 are constants.
2. Expressions and Equations
An algebraic expression is a combination of variables, constants, and operators (like addition, subtraction, multiplication, and division). An equation is a statement that two expressions are equal. For example, \( 3x + 4 \) is an expression, and \( 3x + 4 = 10 \) is an equation.
Example:
The expression \( 2x^2 + 5x - 3 \) involves variables and constants combined with operators.
The equation \( 2x + 3 = 9 \) states that the expression \( 2x + 3 \) is equal to 9.
3. Solving Equations
Solving an equation means finding the value of the variable that makes the equation true. This often involves isolating the variable on one side of the equation. For example, to solve \( 2x + 3 = 9 \), you would first subtract 3 from both sides, then divide by 2 to find \( x \).
Example:
Solve \( 2x + 3 = 9 \):
1. Subtract 3 from both sides: \( 2x = 6 \)
2. Divide both sides by 2: \( x = 3 \)
4. Algebraic Properties
Algebraic properties, such as the commutative, associative, and distributive properties, help simplify and solve equations. For example, the distributive property states that \( a(b + c) = ab + ac \).
Example:
Using the distributive property to simplify \( 3(x + 2) \):
\[ 3(x + 2) = 3x + 6 \]
5. Applications of Algebra
Algebra is used in various real-world applications, such as calculating interest rates, determining distances, and solving problems in physics and engineering. Understanding algebra helps in making predictions and decisions based on mathematical models.
Example:
If you invest $1000 at an annual interest rate of 5% compounded annually for 3 years, you can calculate the future value using the formula \( A = P(1 + r)^t \):
\[ A = 1000(1 + 0.05)^3 \approx 1157.63 \]