Complete the Expression: Finding the Equal Value of 3^(x-y)

Exponent Laws with Subtraction Property

Insert the corresponding expression:

3xy= 3^{x-y}=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:06 Let's get started!
00:08 We're going to use a special formula for dividing powers.
00:13 If you have a number A raised to the power of N, divided by the same number A raised to M,
00:20 it equals A raised to the power of M minus N.
00:24 We'll apply this formula in our exercise.
00:28 Let's match each number to the variables in the formula.
00:38 Now, let's rewrite the problem as a division of powers.
00:51 And that's how we solve this question!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Insert the corresponding expression:

3xy= 3^{x-y}=

2

Step-by-step solution

To solve the problem, we need to understand the Power of a Quotient Rule for Exponents. The rule states that:

  • If you have a power of the quotient, such as: (ab)n (\frac{a}{b})^n , it can also be expressed as: anbn \frac{a^n}{b^n}

In the given expression, we have 3xy 3^{x-y} . This can be rewritten using the inverse of the rule as:

3xy=3x3y 3^{x-y} = \frac{3^x}{3^y}

Here’s a step-by-step breakdown:

  1. Start with the expression: 3xy 3^{x-y} .
  2. Using the law of exponents, which states that amn=aman a^{m-n} = \frac{a^m}{a^n} , we rewrite the expression.
  3. Replace a a with 3 3 , m m with x x , and n n with y y to get: 3xy=3x3y 3^{x-y} = \frac{3^x}{3^y} .

The solution to the question is: 3x3y \frac{3^x}{3^y}

3

Final Answer

3x3y \frac{3^x}{3^y}

Key Points to Remember

Essential concepts to master this topic
  • Law: For subtraction in exponents, use amn=aman a^{m-n} = \frac{a^m}{a^n}
  • Technique: Transform 3xy 3^{x-y} into quotient form 3x3y \frac{3^x}{3^y}
  • Check: Verify by expanding: 3x3y=3x3y=3xy \frac{3^x}{3^y} = 3^x \cdot 3^{-y} = 3^{x-y}

Common Mistakes

Avoid these frequent errors
  • Applying division incorrectly to the base and exponent
    Don't write 3xy=3y3x 3^{x-y} = \frac{3^y}{3^x} or confuse it with 3xy 3^{\frac{x}{y}} ! This reverses the fraction or changes the operation completely. Always remember that subtraction in the exponent means the first term goes in the numerator: 3xy=3x3y 3^{x-y} = \frac{3^x}{3^y} .

Practice Quiz

Test your knowledge with interactive questions

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

FAQ

Everything you need to know about this question

Why does 3xy 3^{x-y} become a fraction?

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When you subtract exponents, you're essentially dividing powers! The law amn=aman a^{m-n} = \frac{a^m}{a^n} shows this relationship clearly. Think of it as: "x minus y" becomes "x divided by y" in exponential form.

How do I remember which term goes on top vs bottom?

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Use this trick: the first term in the subtraction goes on top! In 3xy 3^{x-y} , x comes first, so 3x 3^x goes in the numerator. The second term (y) gives us 3y 3^y in the denominator.

Is 3xy 3^{x-y} the same as (3x)y (3^x)^y ?

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No, they're completely different! 3xy 3^{x-y} means subtract the exponents, while (3x)y (3^x)^y means multiply them: (3x)y=3xy (3^x)^y = 3^{xy} . Don't confuse subtraction with power-to-power rules!

Can I use this rule with different bases?

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This rule works for any base! Whether it's 2ab 2^{a-b} , xmn x^{m-n} , or 10pq 10^{p-q} , they all follow the same pattern: basefirstsecond=basefirstbasesecond \text{base}^{\text{first} - \text{second}} = \frac{\text{base}^{\text{first}}}{\text{base}^{\text{second}}} .

What if the exponent subtraction gives me a negative result?

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That's perfectly fine! If x < y, then 3xy 3^{x-y} will have a negative exponent, which means 3x3y \frac{3^x}{3^y} will be a fraction less than 1. The rule still works the same way!

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