Compare Powers: (10×3)^7 and the Reciprocal of (15×2)^-7

Exponent Rules with Negative Powers

Insert the compatible sign:

>,<,= >,<,=

(10×3)71(15×2)7 (10\times3)^7\Box\frac{1}{\left(15\times2\right)^{-7}}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Insert the appropriate sign
00:04 According to the laws of exponents, a number to the power (N)
00:07 equals the reciprocal number to the power multiplied by (-1)
00:14 Let's apply this formula to our exercise
00:19 Convert to the reciprocal number (1 divided by the number)
00:22 Raise to the power multiplied by (-1)
00:26 Let's insert this into our exercise
00:34 Calculate the multiplication
00:42 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Insert the compatible sign:

>,<,= >,<,=

(10×3)71(15×2)7 (10\times3)^7\Box\frac{1}{\left(15\times2\right)^{-7}}

2

Step-by-step solution

To solve this problem, we'll follow these steps:

  • Step 1: Simplify both expressions using exponent rules.
  • Step 2: Compare the simplified results to determine the appropriate sign.

First, simplify (10×3)7 (10 \times 3)^7 :
According to the power of a product rule, (ab)n=an×bn (ab)^n = a^n \times b^n . So,

(10×3)7=107×37(10 \times 3)^7 = 10^7 \times 3^7.

Now, simplify 1(15×2)7 \frac{1}{(15 \times 2)^{-7}} :
Firstly, address the negative exponent: (ab)n=1an×bn (ab)^{-n} = \frac{1}{a^n \times b^n} , so we have:

(15×2)7=1157×27(15 \times 2)^{-7} = \frac{1}{15^7 \times 2^7}.
Then, taking the reciprocal because of the double negative (when taking the reciprocal of inverse due to n -n ),

1(15×2)7=157×27\frac{1}{(15 \times 2)^{-7}} = 15^7 \times 2^7.

Now, compare the expressions:
Since 10=2×510 = 2 \times 5 and 15=3×515 = 3 \times 5, consider breaking each base into prime factors:

107×37=(27×57)×3710^7 \times 3^7 = (2^7 \times 5^7) \times 3^7,
157×27=(37×57)×2715^7 \times 2^7 = (3^7 \times 5^7) \times 2^7.

Both 107×3710^7 \times 3^7 and 157×2715^7 \times 2^7 resolve to the same product since they are permutations of the same multiplication.

Thus, we conclude:

The two expressions are equal, so the compatible sign is = = .

Therefore, the solution to the problem is = = .

3

Final Answer

=

Key Points to Remember

Essential concepts to master this topic
  • Power of Products: (ab)n=an×bn (ab)^n = a^n \times b^n applies to both expressions
  • Negative Exponents: 1xn=xn \frac{1}{x^{-n}} = x^n so reciprocal flips the sign
  • Prime Factorization: Break down to verify 27×37×57=37×57×27 2^7 \times 3^7 \times 5^7 = 3^7 \times 5^7 \times 2^7

Common Mistakes

Avoid these frequent errors
  • Incorrectly handling negative exponents in reciprocals
    Don't forget that 1xn \frac{1}{x^{-n}} becomes xn x^n , not xn x^{-n} ! Students often keep the negative exponent, getting 1307 \frac{1}{30^7} instead of 307 30^7 . Always remember: taking the reciprocal of a negative exponent makes it positive.

Practice Quiz

Test your knowledge with interactive questions

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

FAQ

Everything you need to know about this question

Why does the reciprocal of a negative exponent become positive?

+

Because reciprocal means "flip"! When you have 1xn \frac{1}{x^{-n}} , you're flipping 1xn \frac{1}{x^n} , which gives you xn x^n . It's like flipping a fraction twice!

How do I know when two expressions with different bases are equal?

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Break them down into prime factors! Like 10=2×5 10 = 2 \times 5 and 15=3×5 15 = 3 \times 5 . When you expand everything, you can see if you get the same combination of prime factors.

Do I always need to use prime factorization for these problems?

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Not always, but it's the most reliable method! Sometimes you can spot patterns quickly, but prime factorization guarantees you won't miss anything and helps you see why expressions are equal.

What if the numbers inside the parentheses are the same?

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If the bases are identical, just compare the exponents directly! But here we have (30)7 (30)^7 in both cases after simplifying, so they're automatically equal.

Can I use a calculator to check my answer?

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Yes, but be careful with very large numbers! 307 30^7 is huge. Instead, try smaller examples first to understand the pattern, then apply the rules.

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