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Polynomials & identities · Ages 13–14

What a polynomial is

A sign goes with the term after it; the degree is the highest term's.

How to do it

Method

A sign goes with the term after it; the degree is the highest term's

4x3 − 2x + 7: three terms, x's coefficient −2, degree 3

Another way

Rewrite it all as adding

4x3 + (−2x) + 7

In full

A monomial is a number, a letter, or a product of numbers and letters: 7, x, −5xy, 3x2. Monomials added together make a polynomial, and each monomial is one of its terms. To read 4x3 − 2x + 7, think of each minus as adding a negative: 4x3 + (−2x) + 7. So its three terms are 4x3, −2x and 7, each sign going with the term after it. The number in front of the letters is the coefficient: −2 for −2x, 1 for x alone, −1 for −x. A term with no letter is the constant term. A term's degree is the sum of its letters' indices (3x2y: 2 + 1 = 3); a polynomial's degree is that of its highest term. Written from the highest power down it is in descending powers; from the lowest up, ascending. Anything with a letter in a denominator (such as 1x) is not a polynomial.

Worked examples

Have a go first, then open each one for the answer and the working.

  1. Example 1

    The degree of the polynomial 4x6 + 5x2y2 − 4 is .

    Show the answer and working

    Answer: 6

    4x6 has degree 6; 5x2y2 has degree 2 + 2 = 4; the constant, 0. A polynomial's degree is its highest term's.

  2. Example 2

    The constant term of the polynomial 2x + 13 + 8x2 is 2.

    True or false?

    Show the answer and working

    Answer: False

    The constant term is the one with no letter: 13. 2 is the coefficient of x.

  3. Example 3

    In the polynomial 6x3 − 9x2 − x − 8, the coefficient of x2 is , the coefficient of x is and the constant term is .

    Fill in each blank

    Show the answer and working

    Answer: −9, −1, −8

    Each sign goes with the term after it: x2's coefficient is −9; x alone has coefficient 1 and −x has −1, so here it is −1; the constant is −8.

Practice questions to try

Try these 5; the answers are at the end. For a whole worksheet, see VIP worksheets below.

  1. 1.The degree of the polynomial 5x3 + 5x4y2 − 15 is .

    Answer:

  2. 2.The constant term of the polynomial 3x + 5 + 4x2 is 5.

    True or false?

    Answer:

  3. 3.In the polynomial 6x2 − 8x + 2, what is the coefficient of x?

    • A. 8
    • B. 6
    • C. −8
    • D. 2

    Choose the right answer

    Answer:

  4. 4.The degree of the polynomial 2x2y − 5x3y4 + 9y7 is .

    Answer:

  5. 5.4x2y2 is a monomial of degree 3.

    True or false?

    Answer:

All the answers
  1. 1. 6
  2. 2. True
  3. 3. C. −8
  4. 4. 7
  5. 5. False
Free worksheet: What a polynomial isWorking out, multiple choice and word problems, with answers and working, to print or save as a PDF

VIP practice notes and papers

Aimed at tests and exams: questions on this topic, new every time, to print or save as a PDF.

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