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## 8th grade (Illustrative Mathematics)

### Course: 8th grade (Illustrative Mathematics) > Unit 7

Lesson 1: Lesson 4: Dividing powers of 10# The 0 & 1st power

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.

## Want to join the conversation?

- how do you type the multiplication symbol on a keyboard?(122 votes)
- 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! :)(300 votes)

- Why any number (except 0 ) raise to power 0 is always 1 ?(14 votes)
- It has to do with the properties of exponents.

Here's a good example:

Lets say you have a number a^x/a^y and x = y.

Using a property of exponents you can rewrite the equation as a^(x-y) and since x=y that becomes a^0.

Also since x = y, a^x = a^y and so it becomes 1/1 or just 1.(4 votes)

- At2:33Sal 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?(11 votes)
- What he showed helped me understand why it does that, so now let me try to explain it for you:

He changed the way he did the exponents to multiplying`1 times`

how many numbers (the number that the exponent is) to that one.

So when it is`2⁰ = 1`

because there aren't any`2`

s to multiply by.

So something as big as`1,000,000⁰ = 1`

Now let's do it regular:

When you have`4⁶ = 1 × 4 × 4 × 4 × 4 × 4 × 4 = 4096`

Well, that is a bit too big of a number so let's do`3² = 1 × 3 × 3 = 9`

Ask me to clarify anything.(21 votes)

- What does the little circle above the 2 mean?(5 votes)
- The circle above is the exponent. The rule is that any number raised to the power of 0 equals to 1. So if 2 or 1,000,000 is raised to the power of 0 it equals 1.(13 votes)

- Why incorporate the 1 at all?(9 votes)
- Because incorporating the 1 helps to give more intuition for why every number raised to the power of 0 equals 1. Sure, you can divide 2 by 2 to get 1, however, you can also say "hey, I have no 2's, but still have the 1."(2 votes)

- (2:26) I really don't understand how any non-zero number to the power of 0 is 1.(7 votes)
- because your not multiplying it by itself any times(0 votes)

- I understood it but now I don’t(7 votes)
- Where did you get the 1?(3 votes)
- 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,(5 votes)

- bruh I understood it for a hot second than you hade to do THIS(6 votes)
- Please help. I don't understand how you get 1 for the answer wouldn't be 2 since you aren't multiplying it by itself?(4 votes)
- Not quite, you see we multiply an exponent by whatever number is in that position ,so if zero is in the position The number multiplies itself zero times ,And that number is just zero . But since there is an invisible one beside the number ,That makes the answer one instead of zero.(3 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.