Algebra Topics

Exponents

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**Exponents** are numbers that have been multiplied by themselves. For instance, **3 · 3 · 3 · 3** could be written as the exponent 3^{4}: the number **3** has been multiplied by itself **4** times.

Exponents are useful because they let us write long numbers in a shortened form. For instance, this number is very large:

1,000,000,000,000,000,000

But you could write it this way as an exponent:

10^{18}

It also works for small numbers with many decimal places. For instance, this number is very small but has many digits:

.00000000000000001

It also could be written as an exponent:

10^{-17}

Scientists often use exponents to convey very large numbers and very small ones. You'll see them often in algebra problems too.

As you saw in the video, exponents are written like this: 4^{3} (you'd read it as **4 to the 3rd power**). All exponents have two parts: the **base**, which is the number being multiplied; and the **power**, which is the number of times you multiply the base.

Because our base is 4 and our power is 3, we’ll need to multiply **4** by itself **three** times.

4^{3} = 4 ⋅ 4 ⋅ 4 = 64

Because **4 · 4 · 4** is 64, **4 ^{3}** is equal to 64, too.

Occasionally, you might see the same exponent written like this: 5^3. Don’t worry, it’s exactly the same number—the base is the number to the left, and the power is the number to the right. Depending on the type of calculator you use—and especially if you’re using the calculator on your phone or computer—you may need to input the exponent this way to calculate it.

How would you simplify these exponents?

7^{1} 7^{0}

Don’t feel bad if you’re confused. Even if you feel comfortable with other exponents, it’s not obvious how to calculate ones with powers of 1 and 0. Luckily, these exponents follow simple rules:

**Exponents with a power of 1**Any exponent with a power of**1**equals the**base**, so 5^{1}is 5, 7^{1}is 7, and x^{1}is*x*.**Exponents with a power of 0**

Any exponent with a power of**0**equals**1**, so 5^{0}is 1, and so is 7^{0}, x^{0}, and any other exponent with a power of 0 you can think of.

How would you solve this problem?

2^{2} ⋅ 2^{3}

If you think you should solve the exponents first, then multiply the resulting numbers, you’re right. (If you weren’t sure, check out our lesson on the order of operations).

How about this one?

x^{3} / x^{2}

Or this one?

2x^{2} + 2x^{2}

While you can’t exactly solve these problems without more information, you can **simplify** them. In algebra, you will often be asked to perform calculations on exponents with variables as the base. Fortunately, it’s easy to add, subtract, multiply, and divide these exponents.

When you’re adding two exponents, you don’t add the actual powers—you add the bases. For instance, to simplify this expression, you would just add the variables. You have two xs, which can be written as **2x**. So, **x ^{2}+x^{2}** would be

x^{2} + x^{2} = 2x^{2}

How about this expression?

3y^{4} + 2y^{4}

You're adding 3y to 2y. Since 3 + 2 is 5, that means that **3y ^{4}** +

3y^{4} + 2y^{4} = 5y^{4}

You might have noticed that we only looked at problems where the exponents we were adding had the same variable and power. This is because you can only add exponents if their bases and exponents are **exactly the same**. So you can add these below because both terms have the same variable (*r*) and the same power (7):

4r^{7} + 9r^{7}

You can **never** add any of these as they’re written. This expression has variables with two different powers:

4r^{3} + 9r^{8}

This one has the same powers but different variables, so you can't add it either:

4r^{2} + 9s^{2}

Subtracting exponents works the same as adding them. For example, can you figure out how to simplify this expression?

5x^{2} - 4x^{2}

**5-4** is 1, so if you said 1*x*^{2}, or simply *x*^{2}, you’re right. Remember, just like with adding exponents, you can only subtract exponents with the **same power and base**.

5x^{2} - 4x^{2} = x^{2}

Multiplying exponents is simple, but the way you do it might surprise you. To multiply exponents, **add the powers**. For instance, take this expression:

x^{3} ⋅ x^{4}

The powers are **3** and **4**. Because **3 + 4** is 7, we can simplify this expression to x^{7}.

x^{3} ⋅ x^{4} = x^{7}

What about this expression?

3x^{2} ⋅ 2x^{6}

The powers are **2** and **6**, so our simplified exponent will have a power of 8. In this case, we’ll also need to multiply the coefficients. The coefficients are 3 and 2. We need to multiply these like we would any other numbers. **3⋅2 is 6**, so our simplified answer is **6x ^{8}**.

3x^{2} ⋅ 2x^{6} = 6x^{8}

You can only simplify multiplied exponents with the same variable. For example, the expression **3x ^{2}⋅2x^{3}⋅4y**

Dividing exponents is similar to multiplying them. Instead of adding the powers, you **subtract** them. Take this expression:

x^{8} / x^{2}

Because **8 - 2** is 6, we know that **x ^{8}/x^{2}** is x

x^{8} / x^{2} = x^{6}

What about this one?

10x^{4} / 2x^{2}

If you think the answer is 5x^{2}, you’re right! **10 / 2** gives us a coefficient of 5, and subtracting the powers (**4 - 2**) means the power is 2.

Sometimes you might see an equation like this:

(x^{5})^{3}

An exponent on another exponent might seem confusing at first, but you already have all the skills you need to simplify this expression. Remember, an exponent means that you're multiplying the **base** by itself that many times. For example, 2^{3} is 2⋅2⋅2. That means, we can rewrite (x^{5})^{3} as:

x^{5}⋅x^{5}⋅x^{5}

To multiply exponents with the same base, simply **add** the exponents. Therefore, x^{5}⋅x^{5}⋅x^{5 }= x^{5+5+5 }= x^{15}.

There's actually an even shorter way to simplify expressions like this. Take another look at this equation:

(x^{5})^{3 }= x^{15}

Did you notice that 5⋅3 also equals 15? Remember, multiplication is the same as adding something more than once. That means we can think of 5+5+5, which is what we did earlier, as 5 times 3. Therefore, when you raise a **power to a power** you can **multiply the exponents**.

Let's look at one more example:

(x^{6})^{4}

Since 6⋅4 = 24, (x^{6})^{4 }= x^{24}

x^{24}

Let's look at one more example:

(3x^{8})^{4}

First, we can rewrite this as:

3x^{8}⋅3x^{8}⋅3x^{8}⋅3x^{8}

Remember in multiplication, order does not matter. Therefore, we can rewrite this again as:

3⋅3⋅3⋅3⋅x^{8}⋅x^{8}⋅x^{8}⋅x^{8}

Since 3⋅3⋅3⋅3 = 81 and x^{8}⋅x^{8}⋅x^{8}⋅x^{8 }= x^{32}, our answer is:

81x^{32}

Notice this would have also been the same as 3^{4}⋅x^{32}.

Still confused about multiplying, dividing, or raising exponents to a power? Check out the video below to learn a trick for remembering the rules:

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