Calculate the Result of the Fractions and Powers: 1/(-3)·3^(-4)·5^3

Negative Exponents with Mixed Operations

Solve the following problem:

133453=? \frac{1}{-3}\cdot3^{-4}\cdot5^3=\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
00:02 According to the laws of exponents, a number (A) raised to the power of (-N)
00:05 equals 1 divided by the number (A) raised to the power of (N)
00:08 Let's apply this to (3) raised to the power of (-4)
00:11 We obtain 1 divided by (3) raised to the power of (4)
00:21 According to the laws of exponents, a number (A) raised to the power of (M)
00:24 multiplied by the same number (A) raised to the power of (N)
00:27 equals the number (A) raised to the power of (M+N)
00:30 Let's apply this to the question and combine the exponents of the denominators
00:35 Let's calculate the power
00:46 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following problem:

133453=? \frac{1}{-3}\cdot3^{-4}\cdot5^3=\text{?}

2

Step-by-step solution

Apply the laws of exponents for negative exponents, in the opposite direction:

1an=an \frac{1}{a^n} = a^{-n}

Thus we can handle the leftmost term in the multiplication:

133453=133453=313453 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-\frac{1}{3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 In the first step we simplified the first fraction whilst remembering that dividing a positive number by a negative number gives a negative result. In the second step we applied the aforementioned law of exponents,

Before we continue, let's note and emphasize that the minus sign is not under the exponent in the first term of the multiplication, meaning - the exponent doesn't apply to it but only to the number 3.

Next, we'll recall the law of exponents for multiplication of terms with identical bases:

aman=am+n a^m\cdot a^n=a^{m+n} and we'll apply this law to the last expression we got:

313453=31+(4)53=31453=3553 -3^{-1}\cdot3^{-4}\cdot5^3=-3^{-1+(-4)}\cdot5^3=-3^{-1-4}\cdot5^3=-3^{-5}\cdot5^3 when we applied the aforementioned law of exponents only to the terms with identical bases and carried the minus sign throughout the calculation for the reason we mentioned earlier,

Let's summarize the steps so far:

133453=313453=31453=3553 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 =-3^{-1-4}\cdot5^3=-3^{-5}\cdot5^3

Note that this answer isn't among the answer choices, however, we can apply the negative exponent law once again:

an=1an a^{-n}=\frac{1}{a^n} We'll apply it to the first term in the multiplication of terms that we obtained in the last step:

3553=13553=5335 -3^{-5}\cdot5^3=-\frac{1}{3^5}\cdot5^3=-\frac{5^3}{3^5} In the first step we applied the aforementioned law to the first term in the multiplication, and in the next step we performed the fraction multiplication whilst remembering that multiplying by a fraction is essentially multiplying by the numerator,

Let's summarize the solution steps again:
133453=313453=3553=5335 \frac{1}{-3}\cdot3^{-4}\cdot5^3=-3^{-1}\cdot3^{-4}\cdot5^3 =-3^{-5}\cdot5^3 =-\frac{5^3}{3^5}

Therefore, the correct answer is answer B.

3

Final Answer

5335 -\frac{5^3}{3^5}

Key Points to Remember

Essential concepts to master this topic
  • Negative Exponents: an=1an a^{-n} = \frac{1}{a^n} converts to positive fractions
  • Technique: 3134=31+(4)=35 3^{-1} \cdot 3^{-4} = 3^{-1+(-4)} = 3^{-5} using multiplication rule
  • Check: Final answer 5335=125243 -\frac{5^3}{3^5} = -\frac{125}{243} matches original calculation ✓

Common Mistakes

Avoid these frequent errors
  • Applying negative sign incorrectly with exponents
    Don't write (3)1 (-3)^{-1} instead of 31 -3^{-1} = wrong base! The negative sign stays outside the exponent and doesn't get raised to the power. Always keep the minus sign separate from the base number.

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 doesn't the negative sign go inside the exponent?

+

The negative sign in 13 \frac{1}{-3} comes from division, not from the base. When we write 31 -3^{-1} , the minus applies to the whole term, while the exponent -1 only applies to the number 3.

How do I multiply terms with the same base but different exponents?

+

Use the rule aman=am+n a^m \cdot a^n = a^{m+n} . For example: 3134=31+(4)=35 3^{-1} \cdot 3^{-4} = 3^{-1+(-4)} = 3^{-5} . Add the exponents when multiplying!

When should I convert negative exponents to fractions?

+

Convert at the end to match answer choices. Work with negative exponents during calculations, then use an=1an a^{-n} = \frac{1}{a^n} for your final answer.

What if I have different bases like 3 and 5?

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You cannot combine terms with different bases using exponent rules. Keep 35 3^{-5} and 53 5^3 separate, then multiply: 3553=5335 3^{-5} \cdot 5^3 = \frac{5^3}{3^5} .

How do I check my answer?

+

Calculate the numerical value: 5335=125243 -\frac{5^3}{3^5} = -\frac{125}{243} . Then verify by computing the original expression step by step to get the same decimal value.

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