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.
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.
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.
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.The degree of the polynomial 5x3 + 5x4y2 − 15 is .
Answer:
2.The constant term of the polynomial 3x + 5 + 4x2 is 5.
True or false?
Answer:
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.The degree of the polynomial 2x2y − 5x3y4 + 9y7 is .
Answer:
5.4x2y2 is a monomial of degree 3.
True or false?
Answer:
All the answers
- 1. 6
- 2. True
- 3. C. −8
- 4. 7
- 5. False
VIP practice notes and papers
Aimed at tests and exams: questions on this topic, new every time, to print or save as a PDF.
- Practice notes: The key point, worked examples step by step, then questions of the same kind to follow, hints fading
- Practice paper: Set out in parts like a school paper, marked, with answers and full working