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Polynomial — Definition and Degree

A polynomial is an algebraic expression made using variables, constants, coefficients, and non-negative whole number powers of variables. The degree is the highest power of the variable present in the polynomial.

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Student-friendly explanation

In one variable, expressions like 3x + 2, - 5x + 6, and 7 are polynomials because the powers of x are whole numbers. Expressions with variables in the denominator or square root of the variable are not polynomials at this level. The degree tells the type of polynomial, such as linear for degree 1 and quadratic for degree 2.

How to write this in exams

  1. 1

    Start with the exact idea

    A polynomial is an algebraic expression made using variables, constants, coefficients, and non-negative whole number powers of variables. The degree is the highest power of the variable present in the polynomial.

  2. 2

    Then show how to use it

    Check each term, note the power of the variable, ensure the powers are non-negative whole numbers, and then choose the highest power as the degree.

  3. 3

    Add one concrete example

    In 5x³ - 2x + 8, the highest power of x is 3, so the degree is 3. In 4x + 9, the degree is 1, so it is linear.

  4. 4

    Avoid this incomplete answer

    For 7x³ + 2x² + 5, a common wrong answer is degree 7 because students look at the largest coefficient instead of the largest exponent.

Definition

A polynomial is an algebraic expression made using variables, constants, coefficients, and non-negative whole number powers of variables. The degree is the highest power of the variable present in the polynomial.

Example

In 5x³ - 2x + 8, the highest power of x is 3, so the degree is 3. In 4x + 9, the degree is 1, so it is linear.

Rule to remember

Polynomial rule: powers of variables must be non-negative whole numbers. Degree in one variable is the highest exponent of the variable.

Memory hook

Degree means highest power, not biggest number.

Examples and method

Worked example

Find the degree of 9 - 3x + 2x⁴. The powers of x are 0 for 9, 1 for -3x, and 4 for 2x⁴. The highest power is 4, so the degree is 4.

Method to apply

Check each term, note the power of the variable, ensure the powers are non-negative whole numbers, and then choose the highest power as the degree.

Diagram support

A term table can be used with columns for term, coefficient, power of variable, and role in expression.

How CBSE asks it

Students may be asked to identify whether an expression is a polynomial, find its degree, or classify it as constant, linear, quadratic, or higher degree.

Avoid common mistakes

Common confusion

Students sometimes count the number of terms as the degree. For example, 2x + 7 has two terms, but its degree is 1, not 2.

Common wrong answer

For 7x³ + 2x² + 5, a common wrong answer is degree 7 because students look at the largest coefficient instead of the largest exponent.

Exam tip

First arrange mentally by powers of the variable, then identify the highest exponent. Do not use the coefficient to decide the degree.

Quick check

What is the degree of the polynomial 6x² - 4x + 1?

The degree is 2 because the highest power of x in 6x² - 4x + 1 is 2.

Study the polynomial — definition and degree diagram carefully

Use the labelled diagram to keep polynomial — definition and degree clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of polynomial — definition and degree in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on polynomial — definition and degree.

Revision cue

Revise polynomial — definition and degree through the labels before writing the answer.

Answer writing and exam use

1-mark answer

A polynomial is an algebraic expression made using variables, constants, coefficients, and non-negative whole number powers of variables. The degree is the highest power of the variable present in the polynomial.

2-mark answer

A polynomial is an algebraic expression made using variables, constants, coefficients, and non-negative whole number powers of variables. The degree is the highest power of the variable present in the polynomial. Polynomial rule: powers of variables must be non-negative whole numbers. Degree in one variable is the highest exponent of the variable. In 5x³ - 2x + 8, the highest power of x is 3, so the degree is 3. In 4x + 9, the degree is 1, so it is linear.

3-mark answer

In one variable, expressions like 3x + 2, - 5x + 6, and 7 are polynomials because the powers of x are whole numbers. Expressions with variables in the denominator or square root of the variable are not polynomials at this level. The degree tells the type of polynomial, such as linear for degree 1 and quadratic for degree 2. Polynomial rule: powers of variables must be non-negative whole numbers. Degree in one variable is the highest exponent of the variable. Find the degree of 9 - 3x + 2x⁴. The powers of x are 0 for 9, 1 for -3x, and 4 for 2x⁴. The highest power is 4, so the degree is 4. Students may be asked to identify whether an expression is a polynomial, find its degree, or classify it as constant, linear, quadratic, or higher degree. For 7x³ + 2x² + 5, a common wrong answer is degree 7 because students look at the largest coefficient instead of the largest exponent.
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