Simplify the Expression: Finding 9^9 ÷ 9^3 Using Power Rules

Division of Powers with Same Base

9993= \frac{9^9}{9^3}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:05 Let's simplify the expression!
00:08 We'll use a formula for dividing with exponents.
00:12 When you divide A to the M by A to the N,
00:16 it equals A raised to the power of M minus N.
00:21 Let's apply this in our exercise now.
00:24 Keep the base the same, subtract the exponents, then calculate.
00:29 And that's how we find the solution. Great job!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

9993= \frac{9^9}{9^3}=

2

Step-by-step solution

Note that in the fraction and its denominator, there are terms with the same base, so we will use the law of exponents for division between terms with the same base:

bmbn=bmn \frac{b^m}{b^n}=b^{m-n}

Let's apply it to the problem:

9993=993=96 \frac{9^9}{9^3}=9^{9-3}=9^6

Therefore, the correct answer is b.

3

Final Answer

96 9^6

Key Points to Remember

Essential concepts to master this topic
  • Rule: When dividing powers with same base, subtract exponents
  • Technique: 9993=993=96 \frac{9^9}{9^3} = 9^{9-3} = 9^6
  • Check: Verify that 96×93=99 9^6 \times 9^3 = 9^9 using multiplication rule ✓

Common Mistakes

Avoid these frequent errors
  • Adding instead of subtracting exponents
    Don't add the exponents like 9 + 3 = 12 to get 912 9^{12} ! This gives a massive wrong answer. Division means we're removing groups, so we subtract. Always use aman=amn \frac{a^m}{a^n} = a^{m-n} for division.

Practice Quiz

Test your knowledge with interactive questions

\( (2^3)^6 = \)

FAQ

Everything you need to know about this question

Why do we subtract exponents when dividing?

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Think of it as canceling out common factors! 99 9^9 means nine 9's multiplied together, and 93 9^3 means three 9's. When we divide, we cancel three 9's from the top, leaving six 9's = 96 9^6 .

What if the bottom exponent is bigger than the top?

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You still subtract! For example, 9399=939=96 \frac{9^3}{9^9} = 9^{3-9} = 9^{-6} . The negative exponent means one over that positive power: 196 \frac{1}{9^6} .

Can I use this rule with different bases like 9 and 3?

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No! The bases must be exactly the same. You can't simplify 9432 \frac{9^4}{3^2} using this rule. However, since 9=32 9 = 3^2 , you could rewrite it first!

How can I check my answer is right?

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Use the multiplication rule backwards! If 9993=96 \frac{9^9}{9^3} = 9^6 is correct, then 96×93 9^6 \times 9^3 should equal 99 9^9 . Since 6 + 3 = 9, it works!

What if there are numbers in front of the powers?

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Handle the coefficients separately! For 699293 \frac{6 \cdot 9^9}{2 \cdot 9^3} , you get 629993=396 \frac{6}{2} \cdot \frac{9^9}{9^3} = 3 \cdot 9^6 . Deal with numbers and powers as separate parts.

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