Class 9 Notes - Polynomials
1. Introduction
A polynomial is an expression consisting of variables, coefficients, and the operations of addition, subtraction, multiplication, and non-negative integer exponents of variables.
2. What is a Polynomial?
A polynomial in one variable is an expression of the form:
a_0 + a_1x + a_2x^2 + ... + a_nx^n
Where x
is the variable, a_0, a_1, ..., a_n
are coefficients, and a_n ≠ 0
.
3. Terms Related to Polynomials
- Term: Part of the expression separated by + or -.
- Coefficient: Numerical factor of a term.
- Degree: Highest power of the variable.
- Constant Polynomial: No variable part.
- Zero Polynomial: Polynomial with value 0.
4. Types of Polynomials Based on Number of Terms
- Monomial: One term
- Binomial: Two terms
- Trinomial: Three terms
- Polynomial: One or more terms
5. Types of Polynomials Based on Degree
Degree |
Name |
Example |
0 | Constant Polynomial | 7, -3 |
1 | Linear Polynomial | 3x + 1 |
2 | Quadratic Polynomial | x² - 4x + 3 |
3 | Cubic Polynomial | x³ + 2x² - 1 |
n | Polynomial of degree n | xⁿ + ... |
6. Algebraic Identities
- (a + b)² = a² + 2ab + b²
- (a - b)² = a² - 2ab + b²
- a² - b² = (a + b)(a - b)
- (x + a)(x + b) = x² + (a + b)x + ab
- (x + y + z)² = x² + y² + z² + 2xy + 2yz + 2zx
- (x + y)³ = x³ + 3x²y + 3xy² + y³
- (x - y)³ = x³ - 3x²y + 3xy² - y³
- x³ + y³ = (x + y)(x² - xy + y²)
- x³ - y³ = (x - y)(x² + xy + y²)
7. Zero of a Polynomial
If p(a) = 0, then a is a zero of the polynomial p(x).
8. Value of a Polynomial
Substitute the variable with the given value to evaluate.
9. Addition and Subtraction of Polynomials
Combine like terms.
10. Multiplication of Polynomials
- Monomial × Monomial
- Monomial × Polynomial
- Binomial × Binomial (Use identities)
- Polynomial × Polynomial
11. Division of Polynomials
Involves long division (basic understanding is enough).
12. Factorization of Polynomials
- Taking out common factors
- Using identities
13. Remainder Theorem
When p(x) is divided by x - a, the remainder is p(a).
14. Factor Theorem
If p(a) = 0, then (x - a) is a factor of p(x).
15. Graphical Meaning of Zeros
Zeros correspond to the x-intercepts of the graph of the polynomial.
16. Applications in Real Life
Used in various fields like physics, engineering, computer science, economics, etc.
17. Summary
- Polynomial: sum of terms with whole number exponents
- Types: monomial, binomial, trinomial
- Operations: add, subtract, multiply
- Identities and factorization are essential tools
- Zeros help solve equations
18. Practice Questions
- Find the degree of the polynomial:
- a) 4x³ + 5x² - 7
- b) 3y⁵ - y + 9
- Factor using identities:
- a) x² - 16
- b) x² + 7x + 10
- Evaluate p(x) = x² - x + 1 at x = -2
- Use Remainder Theorem to find remainder of p(x) = x² + 4x + 3 when divided by x + 1
- Check whether x + 3 is a factor of x² + 5x + 6 using Factor Theorem