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Lesson 6: Algebraic Expressions. Polynomials (II)

January 17, 2011

5. Polynomials

Polynomial is an algebraic sum (this is, addition or subtraction) of monomials.

The terms of polynomial are the monomials that form it. The monomial that has no literal part is called independent term.

Degree of polynomial is the most of degrees of monomials, forming this polynomial.

We obtain the opposite polynomial of P(x), and we write it – P(x), by changing the sign of all the coefficients of the polynomial P(x).

 We use to write polynomials arranging terms so that powers of x are in descending order. Practise this as well as the concept of degree on

Evaluating a polynomial

The arithmetic value of a polynomial P(x for a value x=a, written P(a), is the number obtained when we substitute the variable x by the value a in the polynomial and we simplify the resulting numeric expression by using the order of operations.

6. Operations with polynomials

We are going to learn how to operate with polynomials: addition, subtraction, multiplication and dividing a polynomial by a monomials. Next year we will learn to divide a polynomial by other polynomial, which is more complicated.

6.1. Adding and subtracting polynomials

To add up two polynomials we add up like terms, and write the unlike terms.

To subtract two polynomials we add up the first polynomial the opposite of the second polynomial.

It will be useful to place the like terms in columns.

You can practise these operations on

This other exercises are more complicate.

6.2. Multiplying a polynomial by a monomial

The product of a monomial by a polynomial, is equal to the sum of the products of the monomial by all the terms of the polynomial.

This step is essential to  advance. Practise this skill on this web. http://www.glencoe.com/sec/math/studytools/cgi-bin/msgQuiz.php4?isbn=0-07-825083-8&chapter=8&lesson=6&headerFile=4&state=fl

6.3. Multiplying two polynomials

The product of two polynomials is equal to the sum of the products of each term of the second polynomial by all the terms of the first polynomial.

Notice we are applying the distributive property as many times as we need. So a product of sums is equal to the sum of all possible products of each addend of one sum to each addend of the other sum.

We will apply the distributive property: a·(b + c) = a·b + a·c.

You can practise this operation on

Here you are more exercises.

6.4. Dividing a polynomial by a monomial

To divide a polynomial by a monomial, we divide each term of the polynomial by the monomial.

This is easy. So if you have any doubt go to point 4.2 and repeat the practice.

7. Factoring out common factors

Distributive property allows transform additions or subtractions into products and vice versa.

a·(b + c) = a·b + a·c.

When we move from the left hand side to the right hand side we apply the distributive property and when we move from the right hand side to the left hand side is called factoring out common factor.

Factoring out common factor consists on transforming an expression that contains additions or subtractions into a product.

Read carefully the examples on this page and pracctise with the examples at the end.

8. Special products

 These products are very useful in calculations with algebraic expressions. We will work with binomials; this is the algebraic sum of two monomials.

 8.1. Square of the sum of two algebraic expressions

The square of a sum equals to the square of the first term plus double product of the first term by the second plus the square of the second term.

(a + b)2=a2 + 2ab + b2 

 8.2. Square of the difference of two algebraic expressions

The square of a difference equals to the square of the first term minus double product of the first term by the second plus the square of the second term.

(a – b)2=a2 – 2ab + b2

 8.3. Product of the sum and difference of two algebraic expressions

The product of the sum and difference of two algebraic expressions is equal to the square of the first expression minus the square of the second expression.

(a + b)· (a – b)=a2 – b2

This point is new for you, and it isn’t so complicated. The special products are extremelly useful in algebra. You must domain them. Practise on

8.4. Applications

These equalities, factoring out common factor and other techniques, are useful to transform algebraic expressions consisting on additions and subtractions into products. This process is called factoring or factorizing.

Finally you can watch these videos on operations with polynomials

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