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Grade 9 Notes of Algebraic Expression|| Compulsory Mathematics

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Factorization involves expressing an algebraic expression as a product of simpler terms. Common methods include taking out the greatest common factor, applying formulas like difference of squares, perfect square trinomials, or sum/difference of cubes. For quadratics, splitting the middle term and factoring by grouping are often used, while higher powers and complex expressions rely on special patterns and formulas.

1. Factorization of Simple Expressions

Factorization means writing an expression as a product of simpler expressions.

Common Factor Method: Take out the greatest common factor (GCF).

Example:
6x^2 + 9x
Step 1: Find GCF = 3x
Step 2: Factor out GCF → 3x*(2*x + 3)

2. Difference of Squares

Formula: a^2 - b^2 = (a + b)(a - b)

Example:
x^2 - 9
Step 1: Recognize 9 = 3^2
Step 2: Apply formula → (x + 3)(x - 3)

Example:
x^2 - 4y^2
Step 1: Recognize 4y^2 = (2y)^2
Step 2: Apply formula → (x + 2y)(x - 2*y)

3. Perfect Square Trinomials

Formulas:
a^2 + 2ab + b^2 = (a + b)^2
a^2 - 2ab + b^2 = (a - b)^2

Example:
x^2 + 6x + 9
Step 1: Recognize 6x = 2x3 and 9 = 3^2
Step 2: Apply formula → (x + 3)^2

Example:
y^2 - 10y + 25
Step 1: Recognize 10y = 2y5 and 25 = 5^2
Step 2: Apply formula → (y - 5)^2

4. Factorization of Quadratics

General quadratic: ax^2 + bx + c

Steps to factorize:

Find two numbers whose product = a*c and sum = b

Split the middle term using these numbers

Factor by grouping

Example:
x^2 - 5x + 6
Step 1: Find numbers → -2 and -3 (sum = -5, product = 6)
Step 2: Split middle term → x^2 - 2x - 3x + 6
Step 3: Group → (x^2 - 2x) - (3x - 6)
Step 4: Factor → x(x - 2) - 3*(x - 2)
Step 5: Final factorization → (x - 3)*(x - 2)

5. Sum and Difference of Cubes

Formulas:
a^3 + b^3 = (a + b)(a^2 - ab + b^2)
a^3 - b^3 = (a - b)(a^2 + ab + b^2)

Example:
x^3 - 8y^3
Step 1: Recognize 8y^3 = (2y)^3
Step 2: Apply formula → (x - 2y)(x^2 + 2xy + 4y^2)

Example:
x^3 + y^3
Step 1: Apply formula → (x + y)(x^2 - xy + y^2)

6. Factorization of Higher Powers

Some expressions like a^4 + a^2*b^2 + b^4 can be factorized using the formula:

a^4 + a^2b^2 + b^4 = (a^2 + ab + b^2)(a^2 - ab + b^2)

Example:
x^4 + x^2 + 1
Step 1: Recognize pattern → (x^2)^2 + x^21 + 1^2
Step 2: Apply formula → (x^2 + x + 1)(x^2 - x + 1)

Example:
x^4 + 4y^4
Step 1: Recognize pattern → x^4 + 4y^4 = (x^2 + 2xy + 2y^2)(x^2 - 2xy + 2*y^2)

7. Factorization by Grouping

Group terms in pairs and take common factors.

Example:
x^2 - 10x + 24 + 6y - 9y^2
Step 1: Group terms → (x^2 - 10x + 25) - (1 - 6y + 9y^2)
Step 2: Recognize squares → (x - 5)^2 - (1 - 3y)^2
Step 3: Apply difference of squares → (x - 3y - 4)(x + 3y - 6)

8. Special Cases

Complex expressions with multiple variables can often be factored using:

Difference of squares

Grouping

Sum/difference of cubes

Examples:
x^2 - 4y^2 = (x + 2y)(x - 2y)
x^4 + 4y^4 = (x^2 + 2xy + 2y^2)(x^2 - 2xy + 2y^2)

9. Important Examples of Factorization

1.a^2 - b^2 = (a + b)*(a - b)

2.x^2 - 4y^2 = (x + 2y)(x - 2y)

3.z^2 - 10*z + 25 = (z - 5)^2

4.y^2 + 6*y + 9 = (y + 3)^2

5.a^2 - 2ab + b^2 = (a - b)^2

6.x^2 - 5x + 6 = (x - 2)(x - 3)

7.a^3 - b^3 = (a - b)(a^2 + ab + b^2)

8. x^3 - 8y^3 = (x - 2y)(x^2 + 2xy + 4y^2)

9. x^3 + y^3 = (x + y)(x^2 - xy + y^2)

10.8z^3 - 1 = (2z - 1)(4z^2 + 2*z + 1)

11.8a^3 + 36a^2b + 54ab^2 + 27 = (2a + 3*b)^3

10. Important Tips

Always check for common factors first.

For quadratics, try to split the middle term.

For higher powers, check difference/sum of squares/cubes formulas.

Use grouping carefully if stuck.

11. Important Questions (Step by Step)

Q1. Factorize x^4 + x^2 + 1
Step 1: Recognize pattern → (x^2)^2 + x^21 + 1^2
Step 2: Factor → (x^2 + x + 1)(x^2 - x + 1)

Q2. Factorize x^2 - 10x + 24 + 6y - 9*y^2
Step 1: Group → (x^2 - 10x + 25) - (1 - 6y + 9y^2)
Step 2: Recognize squares → (x - 5)^2 - (1 - 3y)^2
Step 3: Apply difference of squares → (x - 3y - 4)(x + 3*y - 6)

Q3. Factorize x^3 - 8*y^3
Step 1: Recognize 8y^3 = (2y)^3
Step 2: Apply formula → (x - 2y)(x^2 + 2xy + 4*y^2)

Q4. Factorize a^4 + a^2*b^2 + b^4
Step 1: Apply formula → (a^2 + ab + b^2)(a^2 - a*b + b^2)

Q5. Factorize x^3 + y^3
Step 1: Apply formula → (x + y)(x^2 - xy + y^2)

Q6. Factorize 8*z^3 - 1
Step 1: Recognize 8z^3 = (2z)^3
Step 2: Apply formula → (2z - 1)(4z^2 + 2z + 1)

Q7. Factorize x^2 - 4*y^2
Step 1: Apply difference of squares → (x + 2y)(x - 2*y)

Q8. Factorize z^2 - 10*z + 25
Step 1: Recognize perfect square → (z - 5)^2

Q9. Factorize y^2 + 6*y + 9
Step 1: Recognize perfect square → (y + 3)^2

Q10. Factorize x^2 - 5*x + 6
Step 1: Split middle term → x^2 - 2x - 3x + 6
Step 2: Group → (x^2 - 2x) - (3x - 6)
Step 3: Factor → x*(x - 2) - 3*(x - 2)
Step 4: Final → (x - 3)*(x - 2)

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