Algebra help! Using variables.?

Question

Please dont give me the answer, explain it!

define a variable and write an algebraic expression for each phrase!

1. the difference of 8 and a number

2. the sum of 4 and a number

these are just a few questions i need help with!

i dont understand it..

help please!

Answer 1

Variables are useful in mathematics because they allow instructions to be specified in a general way. If we were forced to use actual values, then the instructions would only apply in a more narrow set of situations. For example:

Specify a mathematical definition for finding the number twice that of ANY number: double(x) = x + x.

Now, all we need to do to find the double of a number is replace x with any number we want.

double(1) = 1 + 1 = 2

double(3) = 3 + 3 = 6

double(55) = 55 + 55 = 110

etc.

In the above example, the variable x is a "placeholder" for any number. One important thing we are assuming is that the value of each occurrence of x is the same—that x does not get a new value between the first x and the second x.

The symbol x commonly denotes an unknown variable. Even though any letter can be used, x is the most common choice.

1.  8-x

2.  4+x

.

.

Answer 2

Breakdown the parts of the phrase ... the difference of ... 8 ... a number

There are two static pieces to this phrase: the difference of ... 8

There is one dynamic piece of this phrase (variable): a number

Difference, means distance between two number so you would use a minus sign to replace its phrase ... sum, means total so you would use a plus sign to replace its phrase.

Example: the difference of 12 and a number ... would be put in to mathematical form: 12 - n ... where n could be any number (variable), but 12 and the minus sign are static.

Hope this helps ...

Answer 3

1. 8-A

2. 4+A

Thats some of the easiest stuff ever.

Answer 4

1  let x be the variable     8-x in absolute value(+)

2 4+x

Answer 5

all you have to do is take the phrase and turn it into a problem with numbers instead of words... all you have to do it pick a letter and replace it with "a number"

for example:

the sum of two and a number would be- 2+x

Answer 6

1) 8-x

2) 4+x

Answer 7

a variable is just a letter standing in for a number you don't know yet. when they put them im sentences "the difference of 8" means subtract 8 and "the sum of 4" means add 4. So 1 would be x - 8 and 2 would be x + 4