Calculate (1/20)^(-7): Negative Exponent Expression Evaluation

Negative Exponents with Fractional Bases

Insert the corresponding expression:

(120)7= \left(\frac{1}{20}\right)^{-7}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:07 Let's simplify this problem.
00:11 When a fraction is raised to a power like N,
00:15 both the top and bottom are raised to that same power, N.
00:20 Let's use this rule in our exercise now.
00:26 Remember, one raised to any power is always one.
00:34 For any number raised to a power, N,
00:37 it equals the reciprocal to power N, times negative one.
00:43 Let's apply this in our example now.
00:46 And that's how we find the solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Insert the corresponding expression:

(120)7= \left(\frac{1}{20}\right)^{-7}=

2

Step-by-step solution

To simplify the expression (120)7 \left(\frac{1}{20}\right)^{-7} , we will apply the rule for negative exponents. The key idea is that a negative exponent indicates taking the reciprocal and converting the exponent to a positive:

  • Start with the expression: (120)7 \left(\frac{1}{20}\right)^{-7} .
  • Apply the negative exponent rule: (1a)n=an \left(\frac{1}{a}\right)^{-n} = a^n .
  • For our expression: (120)7 \left(\frac{1}{20}\right)^{-7} becomes 207 20^7 .

Therefore, (120)7 \left(\frac{1}{20}\right)^{-7} simplifies to 207 20^7 .

Thus, the correct answer is 207 20^7 .

3

Final Answer

207 20^7

Key Points to Remember

Essential concepts to master this topic
  • Rule: Negative exponent means flip and make positive
  • Technique: (120)7=207 \left(\frac{1}{20}\right)^{-7} = 20^7 by reciprocal rule
  • Check: Verify by converting back: 207=1(120)7 20^7 = \frac{1}{\left(\frac{1}{20}\right)^7}

Common Mistakes

Avoid these frequent errors
  • Applying negative sign to the entire expression
    Don't think (120)7=207 \left(\frac{1}{20}\right)^{-7} = -20^7 ! The negative exponent doesn't make the answer negative - it indicates reciprocal operation. Always remember: negative exponent means flip the base, not make it negative.

Practice Quiz

Test your knowledge with interactive questions

\( 112^0=\text{?} \)

FAQ

Everything you need to know about this question

Why doesn't the negative exponent make the answer negative?

+

The negative sign in the exponent is an instruction to take the reciprocal, not to make the result negative. Think of it as "flip and make positive" rather than adding a negative sign!

How do I remember the rule for (1a)n \left(\frac{1}{a}\right)^{-n} ?

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Remember: "Flip twice, get back home!" The fraction 120 \frac{1}{20} is already flipped from 20, so the negative exponent flips it back to 207 20^7 .

What's the difference between 207 20^{-7} and 207 20^7 ?

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207=1207 20^{-7} = \frac{1}{20^7} (a very small number), while 207 20^7 is a very large number. The negative exponent creates the reciprocal!

Can I solve this step by step instead of using the rule?

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Yes! You can write: (120)7=1(120)7=11207=207 \left(\frac{1}{20}\right)^{-7} = \frac{1}{\left(\frac{1}{20}\right)^7} = \frac{1}{\frac{1}{20^7}} = 20^7 . Both methods give the same answer!

Does this rule work for any fraction with negative exponents?

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Absolutely! For any fraction (ab)n=(ba)n \left(\frac{a}{b}\right)^{-n} = \left(\frac{b}{a}\right)^n . Just flip the fraction and make the exponent positive!

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