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### Course: Class 6 (Old)>Unit 2

Lesson 6: Identity properties of 0 and 1

# Identity property of 0

Sal shows how any number plus 0 is the original number. Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

• By what do you multiply 1587 to get 1?
• Multiply it by the inverse.

For Example:

X * 1/X=1
• Does negative zero exist?
• No, it's not positive or negative.
• Is the identity property of 0 similar to the identity property of addition or the identity property of multiplication?
• It is a different way of describing the identity property of addition.
• i wonder why letters are in math ?
• The letters are called variables .they are used if we dont know the value of that number.
example - x ,y,z etc.
• Specifically with the properties of 0, I found myself pondering a question about multiplying and dividing by 0.

As a 'rule', any number times 0 is equal to 0. Mathmatically, 0*x=0

Also, as a 'rule', any number divided by 0 is undefined. Mathmatically, x/0 is undefined.

My question stems from the issue of simplifying and resolving complex algebraic equations where an intermediate step may result in dividing by 0 but that portion cancels.

Is 0*(x/0) equal to 0 or undefined?
• If you divide by 0, in any step, it is undefined. This is actually a trick that is often used to prove things like 1=0. ;-)

If you have something like [(x+1)(x-1)]/(x+1), it will be undefined at x=-1, even though the (x+1) cancels.
• I always thought 0 is by far one of the most interesting things in math : 0 multiply something, even if the something is huge, even if it is near an infinite number, will give 0 as a result. Definitely there's something magic behind the zero ! By the way is zero is consider as a "number"? I mean 0 represents nothing. Could we call nothing a number? If not what is the proper term?
• Why is zero in math expressions when all we do is ignore the zero? I was always confused as to why we have zeros in math.
• Zeroes occur in many ways in math. You can't always ignore them.
I can't ignore these zeroes... they all have meaning and/or will affect the math:
205: The 0 fills a place value. Without it the number's value changes. It can't be ignored.
2 * 0 + 5: The zero impacts the math. If you ignore it, you would get 7. The correct answer is 5

These are just a couple of example of why you can't always ignore zeroes.
(1 vote)
• will someone talk to me i have no friends
• What's the difference between the associative and commutative law of addition?
(1 vote)
• Commutative property shows you that you can change the order of the numbers and you will get the same result. This means, if you try to add: `2 + 3 + 5`, you could also do `3 + 2 + 5`, or `5 + 3 + 2` and other variations. All of them will create the same answer. Thus, when you are adding numbers, the order doesn't matter. Add them in whatever order you want.

The Associative Property shows us that we can move the grouping symbols and we will still get the same answer. For example: `3 + (5 + 7)` will create the same answer as `(3 + 5) + 7`. This property only moves the parentheses or other grouping symbols. It will not move the numbers.

Hope this helps.