Grade 11 ↓
Algebra
Algebra is a branch of mathematics that deals with symbols and the rules for manipulating those symbols. In algebra, those symbols (and their arithmetic operations) are used to represent real-world situations.
Basic concepts of algebra
Variables
In algebra, a variable is a symbol used to represent a number. It is usually a letter such as x
, y
, or z
. For example, in the equation x + 2 = 5
, x
is a variable.
Constants
Constants are fixed values. They do not change. Examples of constants include numbers such as 3
, -7
and 10.5
.
Expression
An algebraic expression is a mathematical phrase that can contain numbers, variables, and operation symbols. An example of an algebraic expression is 4x + 7
.
Equation
An algebraic equation is a statement that two algebraic expressions are equal. For example, 3x + 2 = 11
is an equation. Equations can have one or more solutions.
Operations in algebra
Addition and subtraction
Adding or subtracting algebraic terms involves combining like terms. Like terms are terms that have variables raised to the same power. For example:
4x + 3x = 7x
5a - 2a = 3a
Multiplication
When multiplying terms, you multiply the coefficients and add the exponents of the same bases. For example:
2x * 3x = 6x^2
4a * 5b = 20ab
Division
When dividing terms, you divide the coefficients and subtract the exponents of the same bases. For example:
8x^2 / 2x = 4x
15a^3 / 5a = 3a^2
Solving linear equations
Solving equations means finding the value of the variable that makes the equation true. Here is the basic step-by-step method for solving linear equations:
Example 1
Solve the equation 2x + 3 = 11
.
Step 1: Subtract 3 from both sides.
2x + 3 - 3 = 11 - 3
2x = 8
Step 2: Divide both sides by 2.
2x / 2 = 8 / 2
x = 4
Example 2
Solve the equation 5y - 7 = 18
.
Step 1: Add 7 to both sides.
5y - 7 + 7 = 18 + 7
5y = 25
Step 2: Divide both sides by 5.
5y / 5 = 25 / 5
y = 5
Graphs of equations
The graph of an equation is the set of all points that satisfy the equation. For linear equations, this graph is a straight line. For example, the graph of y = 2x + 3
is a straight line.
Polynomials
A polynomial is an expression consisting of variables and coefficients, built using addition, subtraction, multiplication, and non-negative integer exponents of the variables.
Example polynomials
An example of a polynomial is 3x^2 + 2x - 5
. This polynomial has three terms:
3x^2
is called a quadratic term.2x
is called the linear term.-5
is called the constant term.
Factorization of polynomials
Factoring is the process of breaking down a complex expression into simpler factors that can be multiplied to get the original expression back. For example, factoring the polynomial x^2 - 5x + 6
gives:
x^2 - 5x + 6 = (x - 2)(x - 3)
Quadratic equations
A quadratic equation is an equation of the form ax^2 + bx + c = 0
, where a
, b
, and c
are constants, and a ≠ 0
. To solve a quadratic equation, you can use:
- Factoring
- Completing the square
- Quadratic formula
Quadratic formula
The quadratic formula to solve ax^2 + bx + c = 0
is:
x = (-b ± √(b^2 - 4ac)) / (2a)
Example
Solve the equation 2x^2 + 3x - 2 = 0
using the quadratic formula:
a = 2, b = 3, c = -2
Step 1: Plug these into the quadratic formula:
x = (-3 ± √(3^2 - 4 * 2 * -2)) / (2 * 2)
Step 2: Simplify under the square root:
x = (-3 ± √(9 + 16)) / 4
x = (-3 ± √25) / 4
Step 3: Solve for x:
x = (-3 ± 5) / 4
The solutions are:
x = (2) / 4 = 0.5
x = (-8) / 4 = -2
Inequality
Inequalities are mathematical statements that relate expressions that are not necessarily equal. They are usually written with one of the symbols <
, ≤
, >
, ≥
. For example, solving the inequality x + 3 > 5
is the same as solving an equation.
Example
Solve the inequality 2x - 3 < 7
.
Step 1: Add 3 to both sides.
2x - 3 + 3 < 7 + 3
2x < 10
Step 2: Divide both sides by 2.
2x/2 < 10/2
x < 5
Systems of linear equations
A system of linear equations is a set of two or more equations that have the same variables. The solution of a system of equations is a set of values of the variables that satisfy each equation in the system.
Solution methods
There are several ways to solve systems of linear equations:
- Graph
- Replacement
- Elimination
Example (substitution)
Solve the system of equations:
1. x + y = 10
2. 2x - y = 1
Step 1: Solve Equation 1 for y:
y = 10 - x
Step 2: Substitute y in Equation 2:
2x - (10 - x) = 1
Simplify x and solve:
2x - 10 + x = 1
3x = 11
x = 11 / 3
Step 3: Substitute the value of x into Equation 1 to get y:
x + y = 10
11/3 + y = 10
y = 10 - 11/3
y = 30/3 - 11/3
y = 19/3
Conclusion
Algebra serves as a strong foundation for higher-level mathematics and provides techniques for solving a variety of mathematical problems. Through understanding and practicing algebraic concepts such as variables, equations, polynomials, and systems of equations, students can develop strong problem-solving skills that are applicable in both academics and the real world.