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Polynomial Further Mathematics Web Book | Edwin Ogie Library
Polynomial Further Mathematics Web Book
A complete guide to polynomial operations, factor theorem, remainder theorem, and polynomial division, with worked examples, practice exercises, and a 30-question CBT quiz timed for 15 minutes.
Introduction to Polynomials
A polynomial is an algebraic expression made of variables, coefficients and non-negative integer powers. Examples include 2x + 3, x² - 4x + 7, and 5x³ - 2x + 1.
Polynomial topics include addition, subtraction, multiplication, division, factor theorem and remainder theorem.
Degree
The highest power of the variable.
Terms
Parts separated by + or −.
Coefficient
The numerical factor of a term.
Addition of Polynomials
To add polynomials, combine like terms only. Like terms have the same variable and the same power.
Worked examples
Example 1
(2x + 3) + (4x + 5)
Group like terms: 2x + 4x = 6x, 3 + 5 = 8.
Answer: 6x + 8
Example 2
(3x² + 2x - 1) + (x² - 5x + 4)
Combine x² terms, x terms and constants.
Answer: 4x² - 3x + 3
Example 3
(5a² - a + 7) + (2a² + 3a - 9)
Answer: 7a² + 2a - 2
Subtraction of Polynomials
To subtract polynomials, change the signs of the second polynomial and then combine like terms.
Worked examples
Example 1
(5x + 6) - (2x + 1)
Change signs: 5x + 6 - 2x - 1
Answer: 3x + 5
Example 2
(4x² + 3x - 2) - (x² - x + 5)
Change signs and collect terms.
Answer: 3x² + 4x - 7
Example 3
(6a - 2a² + 7) - (3a + a² - 1)
Answer: -3a² + 3a + 8
Multiplication of Polynomials
Multiply each term in one polynomial by each term in the other. Then simplify by combining like terms.
Worked examples
Example 1
(x + 2)(x + 3)
x·x = x², x·3 = 3x, 2·x = 2x, 2·3 = 6
Answer: x² + 5x + 6
Example 2
(2x - 1)(x + 4)
Answer: 2x² + 7x - 4
Example 3
(3a + 2)(a - 5)
Answer: 3a² - 13a - 10
Example 4
(x - 3)²
Answer: x² - 6x + 9
Division of Polynomials
Polynomials can be divided by another polynomial using long division or synthetic division when applicable. The dividend is divided by the divisor to obtain a quotient and sometimes a remainder.
Worked examples
Example 1
(x² + 5x + 6) ÷ (x + 2)
Answer: x + 3
Example 2
(x² - 9) ÷ (x - 3)
Answer: x + 3
Example 3
(2x² + 7x + 3) ÷ (x + 3)
Answer: 2x + 1
Remainder Theorem
The remainder theorem states that when a polynomial f(x) is divided by x - a, the remainder is f(a).
Remainder Theorem: If f(x) is divided by x - a, remainder = f(a).
Worked examples
Example 1
Find the remainder when f(x)=x²+3x+1 is divided by x-2.
Compute f(2) = 4 + 6 + 1 = 11.
Answer: 11
Example 2
Find the remainder when f(x)=2x³-x+4 is divided by x+1.
Compute f(-1) = -2 + 1 + 4 = 3.
Answer: 3
Example 3
Find the remainder when f(x)=x³-4x²+2x-5 is divided by x-3.
Compute f(3) = 27 - 36 + 6 - 5 = -8.
Answer: -8
Factor Theorem
The factor theorem states that x - a is a factor of a polynomial f(x) if and only if f(a)=0.
Factor Theorem: x - a is a factor of f(x) when f(a) = 0.
Worked examples
Example 1
Show that x - 2 is a factor of f(x)=x²-5x+6.
Compute f(2) = 4 - 10 + 6 = 0.
Answer: Yes, it is a factor.
Example 2
Test whether x + 1 is a factor of x³ + x² - x - 1.
Compute f(-1) = -1 + 1 + 1 - 1 = 0.
Answer: Yes, it is a factor.
Example 3
Find k if x - 3 is a factor of x² + kx - 12.
Set f(3)=0: 9 + 3k - 12 = 0.
So, 3k - 3 = 0, hence k = 1.
Example 4
Find the factor of x² - 7x + 12.
It factorizes to (x - 3)(x - 4).
Answer: x - 3 and x - 4 are factors.
20 Exercises
Try the exercises first, then reveal the answers to check your work.
1. Define a polynomial.
2. Find the degree of 5x³ - 2x + 1.
3. Add (2x + 3) and (4x + 1).
4. Subtract (3x + 5) from (7x + 2).
5. Multiply (x + 1)(x + 5).
6. Expand (x - 2)².
7. Divide (x² + 7x + 12) by (x + 3).
8. State the remainder theorem.
9. Find the remainder when x² + 4x + 1 is divided by x - 1.
10. Test if x - 2 is a factor of x² - 5x + 6.
11. Find the remainder when 2x³ - x + 4 is divided by x + 1.
12. Factorize x² - 9.
13. Factorize x² + 5x + 6.
14. Find k if x - 1 is a factor of x² + kx - 2.
15. Find the degree of 3x⁴ + x² - 6.
16. Multiply (2x - 3)(x + 4).
17. Subtract (x² - 2x + 1) from (3x² + x - 4).
18. What is the coefficient of x² in 7x² - 4x + 9?
19. If f(3)=0, what does that tell you?
20. Find the quotient of (x² - 4x + 4) ÷ (x - 2).
CBT Quiz
30 questions | 15 minutes | One question at a time
Quiz Result
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