Simplify the Complex Fraction: Dividing Powers and Managing Negative Exponents

Exponential Comparison with Negative Exponents

727873(7)4——727973(7)4 \frac{7^2\cdot7^{-8}}{7^3\cdot(-7)^4}_{——}\frac{7^2\cdot7^{-9}}{7^3\cdot(-7)^4}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Select the appropriate sign
00:03 When multiplying powers with equal bases
00:08 The power of the result equals the sum of the powers
00:12 We'll apply this formula to our exercise, let's add up the powers
00:23 We'll do the same thing on the right side of the exercise
00:31 Let's calculate the powers
00:53 In order to eliminate a negative power
00:56 We'll invert the numerator and denominator and the power will become positive
00:59 We'll apply this formula to our exercise, and transfer from the numerator to the denominator
01:23 Let's identify where the power is larger
01:30 Only this power changes because the rest of the exercise is the same
01:38 The larger power is in the denominator, therefore it's smaller
01:42 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

727873(7)4——727973(7)4 \frac{7^2\cdot7^{-8}}{7^3\cdot(-7)^4}_{——}\frac{7^2\cdot7^{-9}}{7^3\cdot(-7)^4}

2

Step-by-step solution

Let's systematically simplify both expressions and then compare them:

Simplifying the First Expression:

727873(7)4\frac{7^2 \cdot 7^{-8}}{7^3 \cdot (-7)^4}

  • Apply Product of Powers Rule to the numerator: 7278=72+(8)=767^2 \cdot 7^{-8} = 7^{2 + (-8)} = 7^{-6}.

  • Use Power of a Power Rule in the denominator for (7)4=(1)474=74(-7)^4 = (-1)^4 \cdot 7^4 = 7^4 because (1)4=1(-1)^4 = 1.

  • Simplify the denominator: 7374=73+4=777^3 \cdot 7^4 = 7^{3+4} = 7^7.

  • Apply Quotient of Powers Rule: 7677=767=713\frac{7^{-6}}{7^7} = 7^{-6-7} = 7^{-13}.

Simplifying the Second Expression:

727973(7)4\frac{7^2 \cdot 7^{-9}}{7^3 \cdot (-7)^4}

  • Apply Product of Powers Rule to the numerator: 7279=72+(9)=777^2 \cdot 7^{-9} = 7^{2 + (-9)} = 7^{-7}.

  • The denominator is the same as before: 7374=777^3 \cdot 7^4 = 7^7.

  • Apply Quotient of Powers Rule: 7777=777=714\frac{7^{-7}}{7^7} = 7^{-7-7} = 7^{-14}.

Comparison:

  • The first expression simplifies to 7137^{-13}.

  • The second expression simplifies to 7147^{-14}.

  • Since 13>14-13 > -14,
    713>7147^{-13} > 7^{-14}.

Therefore, the first expression is greater than the second expression. The correct choice is: > > .

3

Final Answer

> >

Key Points to Remember

Essential concepts to master this topic
  • Rule: Combine like bases using aman=am+n a^m \cdot a^n = a^{m+n}
  • Technique: Recognize (7)4=74 (-7)^4 = 7^4 since even power makes positive
  • Check: Verify 713=1713>1714=714 7^{-13} = \frac{1}{7^{13}} > \frac{1}{7^{14}} = 7^{-14}

Common Mistakes

Avoid these frequent errors
  • Treating (-7)^4 as negative
    Don't treat (7)4 (-7)^4 as negative = wrong denominator! Even powers always give positive results, so (7)4=74 (-7)^4 = 7^4 . Always remember that (a)even=aeven (-a)^{even} = a^{even} and (a)odd=aodd (-a)^{odd} = -a^{odd} .

Practice Quiz

Test your knowledge with interactive questions

Simplify the following equation:

\( \)\( 4^5\times4^5= \)

FAQ

Everything you need to know about this question

Why is 7^(-13) greater than 7^(-14)?

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With negative exponents, less negative means bigger! Think of it as fractions: 713=1713 7^{-13} = \frac{1}{7^{13}} and 714=1714 7^{-14} = \frac{1}{7^{14}} . Since 714>713 7^{14} > 7^{13} , we have 1713>1714 \frac{1}{7^{13}} > \frac{1}{7^{14}} .

How do I handle (-7)^4?

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Even powers make everything positive! So (7)4=74 (-7)^4 = 7^4 . Remember: negative base with even exponent = positive result, but negative base with odd exponent stays negative.

What's the fastest way to simplify these fractions?

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Use the exponent rules systematically: First combine powers in numerator (aman=am+n a^m \cdot a^n = a^{m+n} ), then in denominator, finally use quotient rule (aman=amn \frac{a^m}{a^n} = a^{m-n} ).

Can I convert to decimals to compare?

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You could, but it's unnecessary work! Since both expressions have the same base (7), just compare the exponents directly. For positive bases, am>an a^m > a^n when m>n m > n .

What if I get confused with all the negative signs?

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Work step by step and write every step clearly. Handle the negative base (7)4 (-7)^4 first, then focus on the exponent rules. Don't try to do everything at once!

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