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8th grade

Course: 8th gradeย >ย Unit 1

Lesson 5: Exponents with negative bases
Math
8th grade
Numbers and operations
Exponents with negative bases
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The 0 & 1st power

Google Classroom
Different ways of thinking about exponents. Raising a number to an exponent means multiplying that number by itself a certain number of times. Any non-zero number raised to the zero power will be equal to one, and that any number raised to the first power will be equal to itself. Created by Sal Khan.

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  • leafers ultimate style avatar for user benjamin
    Posted 10 years ago. Direct link to benjamin's post โ€œhow do you type the multi...โ€
    how do you type the multiplication symbol on a keyboard?
    (122 votes)
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    • female robot ada style avatar for user Alima Ahmed
      Posted 10 years ago. Direct link to Alima Ahmed's post โ€œWell, there are two ways ...โ€
      Incredible Answer
      Great Answer
      Good Answer
      Well, there are two ways that I know of:
      - An asterix = * (which, by the way, is from a Greek root word that means "little star") You can usually find it where your numbers are on your keyboard. Ex: 12 * 6 = 72
      - A lower case X = x. I don't think I have to tell you where that is on a keyboard! Ex: 12 x 8 = 96
      Also as a footnote to this, "x" will sometimes not work because it could also represent a variable. So be careful!
      Hope this helps! :)
      (297 votes)
  • piceratops ultimate style avatar for user RITIK BOMPILWAR
    Posted 10 years ago. Direct link to RITIK BOMPILWAR's post โ€œWhy any number (except 0 ...โ€
    Why any number (except 0 ) raise to power 0 is always 1 ?
    (14 votes)
    Default Khan Academy avatar avatar for user
  • starky ultimate style avatar for user Rainbow of the Lionhearts
    Posted 7 years ago. Direct link to Rainbow of the Lionhearts's post โ€œAt 2:33 Sal says it will ...โ€
    At
    2:33
    Sal says it will make sense. I never really got past the 2 to the 0 power. I don't understand how he took two, put a zero above it, and then turned it into a one?! How does that work?
    (12 votes)
    Default Khan Academy avatar avatar for user
  • blobby green style avatar for user EricSoTuff229
    Posted 4 months ago. Direct link to EricSoTuff229's post โ€œโ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„...โ€
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–‘โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–Œโ–’โ–ˆโ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–€โ–’โ–Œโ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–Œโ–’โ–’โ–ˆโ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–€โ–’โ–’โ–’โ–โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–โ–„โ–€โ–’โ–’โ–€โ–€โ–€โ–€โ–„โ–„โ–„โ–€โ–’โ–’โ–’โ–’โ–’โ–โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–„โ–„โ–€โ–’โ–‘โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–ˆโ–’โ–’โ–„โ–ˆโ–’โ–โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–„โ–€โ–’โ–’โ–’โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–€โ–ˆโ–ˆโ–€โ–’โ–Œโ–‘โ–‘โ–‘
    โ–‘โ–‘โ–โ–’โ–’โ–’โ–„โ–„โ–’โ–’โ–’โ–’โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–€โ–„โ–’โ–’โ–Œโ–‘โ–‘
    โ–‘โ–‘โ–Œโ–‘โ–‘โ–Œโ–ˆโ–€โ–’โ–’โ–’โ–’โ–’โ–„โ–€โ–ˆโ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–ˆโ–’โ–โ–‘โ–‘
    โ–‘โ–โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–Œโ–ˆโ–ˆโ–€โ–’โ–’โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–€โ–„โ–Œโ–‘
    โ–‘โ–Œโ–‘โ–’โ–„โ–ˆโ–ˆโ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–’โ–Œโ–‘
    โ–โ–’โ–€โ–โ–„โ–ˆโ–„โ–ˆโ–Œโ–„โ–‘โ–€โ–’โ–’โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–โ–‘
    โ–โ–’โ–’โ–โ–€โ–โ–€โ–’โ–‘โ–„โ–„โ–’โ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–’โ–’โ–’โ–Œ
    โ–โ–’โ–’โ–’โ–€โ–€โ–„โ–„โ–’โ–’โ–’โ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–’โ–โ–‘
    โ–‘โ–Œโ–’โ–’โ–’โ–’โ–’โ–’โ–€โ–€โ–€โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–’โ–’โ–Œโ–‘
    โ–‘โ–โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–’โ–„โ–’โ–’โ–โ–‘โ–‘
    โ–‘โ–‘โ–€โ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–‘โ–’โ–‘โ–’โ–‘โ–’โ–„โ–’โ–’โ–’โ–’โ–Œโ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–€โ–„โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–„โ–„โ–„โ–€โ–’โ–’โ–’โ–’โ–„โ–€โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–€โ–„โ–„โ–„โ–„โ–„โ–„โ–€โ–€โ–€โ–’โ–’โ–’โ–’โ–’โ–„โ–„โ–€โ–‘โ–‘โ–‘โ–‘โ–‘
    โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–’โ–€โ–€โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘โ–‘ lol ok
    (21 votes)
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  • cacteye yellow style avatar for user Karlar
    Posted 9 years ago. Direct link to Karlar's post โ€œWhat does the little circ...โ€
    What does the little circle above the 2 mean?
    (6 votes)
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  • blobby green style avatar for user Anne Kozlowski
    Posted 4 months ago. Direct link to Anne Kozlowski's post โ€œWhy incorporate the 1 at ...โ€
    Why incorporate the 1 at all?
    (10 votes)
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  • ohnoes default style avatar for user Dakota Bailey
    Posted 4 years ago. Direct link to Dakota Bailey's post โ€œ(2:26) I really don't und...โ€
    (
    2:26
    ) I really don't understand how any non-zero number to the power of 0 is 1.
    (8 votes)
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  • female robot grace style avatar for user nymphachan
    Posted 10 years ago. Direct link to nymphachan's post โ€œWhere did you get the 1?โ€
    Where did you get the 1?
    (4 votes)
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    • blobby green style avatar for user Larry Kuck
      Posted 10 years ago. Direct link to Larry Kuck's post โ€œHello, We are permitted t...โ€
      Hello,
      We are permitted to multiply by 1 because it does not change the outcome, whether it's a simple multiplication problem of
      3 x 3 = 1 x 3 x 3 = 9
      or explaining why
      n^0 = 1
      where n is any number.

      Just as multiplying by 1 does not change the outcome, not multiplying by 1 should produce the same outcome that was reached by multiplying by 1.

      I see many people are asking the same or similar questions, and I provided a similar, but more detailed response to the first question under this video,
      (6 votes)
  • blobby green style avatar for user Deepak Somarajan
    Posted 3 years ago. Direct link to Deepak Somarajan's post โ€œif 2^0 is 1, would 0^0 be...โ€
    if 2^0 is 1, would 0^0 be 1, 0, or undefined?
    (6 votes)
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    • primosaur seed style avatar for user Ian Pulizzotto
      Posted 3 years ago. Direct link to Ian Pulizzotto's post โ€œInteresting question! Co...โ€
      Interesting question!

      Consider the following two rules.

      1) Any nonzero number to the 0 power is 1.

      2) Zero to any positive power is 0.

      If we attempt to extend both of these rules to define 0^0, we get two different answers. Because of this situation, it is best to call 0^0 indeterminate (though 0^0 is often interpreted as 1).

      Have a blessed, wonderful day!
      (3 votes)
  • leaf green style avatar for user EUNJY KIM
    Posted 8 years ago. Direct link to EUNJY KIM's post โ€œAt Korea, we learned 2^0 ...โ€
    At Korea, we learned 2^0 is 0. Why is it different?
    (7 votes)
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    • starky ultimate style avatar for user apatro2
      Posted 2 years ago. Direct link to apatro2's post โ€œwell here we learn it lik...โ€
      well here we learn it like this
      3*3=9 and then to make sure we divide it by the 3 we divide it by the three because that is the number that is being multiplied so if we do something like 10 to the third it would be 1000 then if we did 10 to the second it would be 100 and 10 to the first be 10 and then 10 to the 0 would be 1 because it is being divided by 10
      (0 votes)

Video transcript

What I want to do in this video is think about exponents in a slightly different way that will be useful for different contexts and also go through a lot more examples. So in the last video, we saw that taking something to an exponent means multiplying that number that many times. So if I had the number negative 2 and I want to raise it to the third power, this literally means taking three negative 2's, so negative 2, negative 2, and negative 2, and then multiplying them. So what's this going to be? Well, let's see. Negative 2 times negative 2 is positive 4, and then positive 4 times negative 2 is negative 8. So this would be equal to negative 8. Now, another way of thinking about exponents, instead of saying you're just taking three negative 2's and multiplying them, and this is a completely reasonable way of viewing it, you could also view it as this is a number of times you're going to multiply this number times 1. So you could completely view this as being equal to-- so you're going to start with a 1, and you're going to multiply 1 times negative 2 three times. So this is times negative 2 times negative 2 times negative 2. So clearly these are the same number. Here we just took this, and we're just multiplying it by 1, so you're still going to get negative 8. And this might be a slightly more useful idea to get an intuition for exponents, especially when you start taking things to the 1 or 0 power. So let's think about that a little bit. What is positive 2 to the-- based on this definition-- to the 0 power going to be equal to? Well, we just said. This says how many times are going to multiply 1 times this number? So this literally says, I'm going to take a 1, and I'm going to multiply by 2 zero times. Well, if I want to multiply it by 2 zero times, that means I'm just left with the 1. So 2 to the zero power is going to be equal to 1. And, actually, any non-zero number to the 0 power is 1 by that same rationale. And I'll make another video that will also give a little bit more intuition on there. That might seem very counterintuitive, but it's based on one way of thinking about it is thinking of an exponent as this. And this will also make sense if we start thinking of what 2 to the first power is. So let's go to this definition we just gave of the exponent. We always start with a 1, and we multiply it by the 2 one time. So 2 is going to be 1-- we're only going to multiply it by the 2. I'll use this for multiplication. I'll use the dot. We're only going to multiply it by 2 one time. So 1 times 2, well, that's clearly just going to be equal to 2. And any number to the first power is just going to be equal to that number. And then we can go from there, and you will, of course, see the pattern. If we say what 2 squared is, well, based on this definition, we start with a 1, and we multiply it by 2 two times. So times 2 times 2 is going to be equal to 4. And we've seen this before. You go to 2 to the third, you start with the 1, and then multiply it by 2 three times. So times 2 times 2 times 2. This is going to give us positive 8. And you probably see a pattern here. Every time we multiply by 2-- or every time, I should say, we raise 2 to one more power, we are multiplying by 2. Notice this, to go from 2 to the 0 to 2 to the 1, we multiplied by 2. I'll use a little x for the multiplication symbol now, a little cross. And then to go from 2 to the first power to 2 to the second power, we multiply by 2 and multiply by 2 again. And that makes complete sense because this is literally telling us how many times are we going to take this number and-- how many times are we going take 1 and multiply it by this number? And so when you go from 2 to the second power to 2 to the third, you're multiplying by 2 one more time. And this is another intuition of why something to the 0 power is equal to 1. If you were to go backwards, if, say, we didn't know what 2 to the 0 power is and we were just trying to figure out what would make sense, well, when we go from 2 to the third power to 2 to the second, we'd be dividing by 2. We're going from 9 to 4. Then we'd divide by 2 again to go from 2 to the second to 2 to the first. And then it seems like we should just divide by 2 again from going from 2 to the first to 2 to the 0. And that would give us 1.