Mastering Class 9 Polynomials
Polynomial Characteristics
What Makes a Polynomial?
In algebra, we work with all sorts of expressions. A polynomial is a special type. Think of it as an expression built from variables and coefficients, using only addition, subtraction, and multiplication, where the variable is raised to non-negative integer powers.
The key rule for an expression to be a polynomial in one variable (like ) is that the exponents of the variable must be [{
}] (0, 1, 2, 3, and so on). No fractions or negative numbers allowed in the exponent!
Let's break down an example: $4x^3 - 2x + 7$.
This polynomial is made up of individual parts called terms, which are separated by plus or minus signs. The terms here are $4x^3$, $-2x$, and $7$.
Within each term, the number part is called the coefficient. In $4x^3$, the coefficient is 4. In $-2x$, it's -2. The term without a variable, 7, is called the constant term.
| Expression | Is it a Polynomial? | Why? |
|---|---|---|
| Yes | All exponents (2, 1, and 0 for the constant term) are whole numbers. | |
| Yes | The exponent on is 4. is just a coefficient. | |
| No | The term is the same as , which has a negative exponent. | |
| No | The term is the same as , which has a fractional exponent. |
Special Cases
Most polynomials have variables, but not all. A number by itself, like 5, is also a polynomial. It's called a constant polynomial. You can think of it as , and since , it simplifies to just 5.
The number 0 is also a polynomial, but it's a very special case called the because it has some unique properties that set it apart from all other constants.
Classifying Polynomials
We can categorize polynomials in two main ways: by how many terms they have, and by their degree.
Degree
noun
The highest exponent of the variable in a polynomial.
The degree tells us the general shape and complexity of the polynomial's graph. Based on the degree, we have special names for the most common types.
| Degree | Name | Example |
|---|---|---|
| 1 | Linear | |
| 2 | Quadratic | |
| 3 | Cubic | |
| 0 | Constant |
We also classify polynomials by their number of terms.
| Number of Terms | Name | Example |
|---|---|---|
| 1 | Monomial | |
| 2 | Binomial | |
| 3 | Trinomial |
An expression can be classified both ways. For example, is a quadratic binomial. It's quadratic because its degree is 2, and it's a binomial because it has two terms. What about ? That's a cubic monomial.
Which of the following expressions is a polynomial?
In the polynomial , what is the coefficient of the term?