Grade 11

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.

x = 3 Solution

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.

y = 2x + 3

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.


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