Calculate (2/3)^-4: Solving Negative Power of a Fraction

Negative Exponents with Fractional Bases

(23)4=? (\frac{2}{3})^{-4}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve the following problem
00:03 According to the laws of exponents, fraction (A\B) to the power of (-N)
00:06 equals fraction (B\A) to the power of (N)
00:10 Let's apply this to our question
00:13 We obtain the fraction (3\2) to the power of (4)
00:17 According to the laws of exponents, any fraction to the power of (N)
00:20 is equal to the numerator to the power of (N) divided by the denominator to the power of (N)
00:23 Let's apply this to the question
00:26 We obtained (3) to the power of 4 divided by (2) to the power of 4
00:29 Let's solve 3 to the power of 4 using the laws of exponents
00:34 Let's solve 2 to the power of 4 using the laws of exponents
00:41 Insert the results
00:46 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

(23)4=? (\frac{2}{3})^{-4}=\text{?}

2

Step-by-step solution

We use the formula:

(ab)n=(ba)n (\frac{a}{b})^{-n}=(\frac{b}{a})^n

Therefore, we obtain:

(32)4 (\frac{3}{2})^4

We use the formula:

(ba)n=bnan (\frac{b}{a})^n=\frac{b^n}{a^n}

Therefore, we obtain:

3424=3×3×3×32×2×2×2=8116 \frac{3^4}{2^4}=\frac{3\times3\times3\times3}{2\times2\times2\times2}=\frac{81}{16}

3

Final Answer

8116 \frac{81}{16}

Key Points to Remember

Essential concepts to master this topic
  • Rule: Negative exponent flips the fraction and makes exponent positive
  • Technique: (23)4=(32)4 (\frac{2}{3})^{-4} = (\frac{3}{2})^4 then calculate normally
  • Check: Multiply result by original base raised to positive power: 8116×(23)4=1 \frac{81}{16} \times (\frac{2}{3})^4 = 1

Common Mistakes

Avoid these frequent errors
  • Making the entire result negative
    Don't think the negative exponent makes the answer negative = 8116 -\frac{81}{16} ! Negative exponents only flip fractions, they don't make results negative. Always remember that negative exponents create reciprocals, not negative numbers.

Practice Quiz

Test your knowledge with interactive questions

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

FAQ

Everything you need to know about this question

Why does a negative exponent flip the fraction?

+

A negative exponent means "take the reciprocal and use the positive exponent". So (23)4 (\frac{2}{3})^{-4} becomes (32)4 (\frac{3}{2})^4 - we flip first, then calculate!

How do I calculate (32)4 (\frac{3}{2})^4 step by step?

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Use the rule (ab)n=anbn (\frac{a}{b})^n = \frac{a^n}{b^n} . So (32)4=3424=8116 (\frac{3}{2})^4 = \frac{3^4}{2^4} = \frac{81}{16} . Calculate top and bottom separately: 34=81 3^4 = 81 and 24=16 2^4 = 16 .

Will the answer always be bigger than 1 with negative exponents?

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When the original fraction is less than 1 (like 23 \frac{2}{3} ), flipping it gives a fraction greater than 1, so yes! But if you started with 53 \frac{5}{3} , flipping would give 35 \frac{3}{5} (less than 1).

What's the difference between (23)4 (\frac{2}{3})^{-4} and (23)4 -(\frac{2}{3})^4 ?

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Huge difference! (23)4=8116 (\frac{2}{3})^{-4} = \frac{81}{16} (positive), but (23)4=1681 -(\frac{2}{3})^4 = -\frac{16}{81} (negative). The placement of the negative sign completely changes the meaning!

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