Easy Algebra Step-by-Step

28 Easy Algebra Step-by-Step

Rules 5, 6, and 7 tell you how to multiply two numbers, but often you will

want to fi nd the product of more than two numbers. To do this, multiply in

pairs. You can keep track of the sign as you go along, or you simply can use

the following guideline:

When 0 is one of the factors, the product

is always 0; otherwise, products that have an

even number of negative factors are positive,

whereas those that have an odd number of neg-

ative factors are negative.

Problem Find the product.

a. ()())()( ())()(

b. ()))()(( )()( )(())(())()(

c. ()))()(( ())(()))()((

Solution

a. ()())()( ())()(

Step 1. 0 is one of the factors, so the product is 0.

()^600 ()−^40 ()−^1000 ()^0 ()^300

b. ()))()(( )()( )(())(())()(

Step 1. Find the product ignoring the signs.

()^3 ()^10 ()^5 ()^25 ()^1 ()^2 =^7500

Step 2. You have fi ve negative factors, so make the product negative.

()− )(()− )(()− ()()−)()(− =− 7500

c. ()−)()(− ()− ())()(−

Step 1. Find the product ignoring the signs.

() 2 () 4 () 10 () 1 () 20 = 1600

Step 2. You have four negative factors, so leave the product positive.

()− )()()− 4 ()(− )()( ()− = 1600

Notice that if there is no zero factor, then

the sign of the product is determined by

how many negative factors you have.