Solve: Fraction Division with Negative 5 Cubed in Denominator (10/(-5)³)

Fraction Division with Negative Exponents

Solve the following problem:

10(5)3=? \frac{10}{(-5)^3}=\text{?}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Simplify the following problem
00:05 When there's a power on a product of elements, all of them are raised to that power
00:13 We'll apply this formula to our exercise
00:20 Factor -5 into -1 and 5
00:28 Remove the minus
00:33 1 divided by the number (A) raised to the power (N)
00:37 Equals the same base with the same exponent in the negative form
00:42 We'll apply this formula to our exercise
00:51 Factor 10 into 2 and 5
00:56 When multiplying powers with equal bases
01:02 The power of the result equals the sum of the powers
01:04 We'll apply this formula to our exercise
01:08 Multiply the powers
01:14 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:

10(5)3=? \frac{10}{(-5)^3}=\text{?}

2

Step-by-step solution

Note that:

a.

10=52 10=5\cdot2

Recall the law of exponents for a multiplication operating inside of parentheses:

(ab)n=anbn (a\cdot b)^n=a^n\cdot b^n

According to this, we obtain the following:

(5)3=(15)3=(1)353=153=53 (-5)^3=(-1\cdot5)^3=(-1)^3\cdot5^3=-1\cdot5^3=-5^3

We want to use the knowledge in 'a' in order to obtain terms with identical bases in both the numerator and denominator,

Let's return to the problem and apply the knowledge obtained from both 'a' and 'b':

10(5)3=2553=21553=2553 \frac{10}{(-5)^3}=\frac{2\cdot5}{-5^3}=\frac{2}{-1}\cdot\frac{5}{5^3}=-2\cdot\frac{5}{5^3}

In the first stage we used 'a' in the numerator and 'b' in the fraction's denominator. In the next stage we presented the fraction as a multiplication of fractions according to the rule for multiplying fractions, then we proceeded to simplify the first fraction in the multiplication.

Now we'll apply the law of exponents for division between terms with identical bases:

aman=amn \frac{a^m}{a^n}=a^{m-n}

Apply this law to the expression as shown below:

2553=2513=252 -2\cdot\frac{5}{5^3}=-2\cdot5^{1-3}=-2\cdot5^{-2}

In the first stage we applied this law to the fraction in the multiplication and then proceeded to simplify the expression that we obtained,

Let's summarize the various steps of the solution:

10(5)3=2553=252 \frac{10}{(-5)^3} =-2\cdot\frac{5}{5^3} =-2\cdot5^{-2}

Therefore, the correct answer is answer b.

3

Final Answer

2(5)2 -2(-5)^{-2}

Key Points to Remember

Essential concepts to master this topic
  • Rule: (a)n=an (-a)^n = -a^n when n is odd
  • Technique: Factor numerator to match base: 10=25 10 = 2 \cdot 5 , then simplify
  • Check: 252=2125=225 -2 \cdot 5^{-2} = -2 \cdot \frac{1}{25} = -\frac{2}{25}

Common Mistakes

Avoid these frequent errors
  • Forgetting that odd exponents preserve negative signs
    Don't calculate (5)3=125 (-5)^3 = 125 = positive result! This ignores the negative base with odd power. Always remember (5)3=125 (-5)^3 = -125 because odd exponents keep the negative sign.

Practice Quiz

Test your knowledge with interactive questions

Insert the corresponding expression:

\( \left(\frac{1}{20}\right)^{-7}= \)

FAQ

Everything you need to know about this question

Why does (5)3 (-5)^3 equal 53 -5^3 ?

+

When you have a negative base with an odd exponent, the result stays negative. Think of it as: (5)3=(5)×(5)×(5)=125 (-5)^3 = (-5) \times (-5) \times (-5) = -125 , which equals 53 -5^3 .

How do I factor the numerator to match the denominator base?

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Look for common factors! Since 10=2×5 10 = 2 \times 5 and our denominator has base 5, we can separate: 10(5)3=2×553 \frac{10}{(-5)^3} = \frac{2 \times 5}{-5^3} .

What does 52 5^{-2} mean exactly?

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Negative exponents mean reciprocals! So 52=152=125 5^{-2} = \frac{1}{5^2} = \frac{1}{25} . It's the same as flipping the base to the denominator with a positive exponent.

Why can't I just divide 10 by -125 directly?

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You absolutely can! 10125=10125=225 \frac{10}{-125} = -\frac{10}{125} = -\frac{2}{25} . But the question asks for the answer in the form 252 -2 \cdot 5^{-2} , which is an equivalent expression showing the exponent laws.

How do I know which answer choice is correct?

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Calculate each choice's numerical value and compare! The correct answer 252=2125=225 -2 \cdot 5^{-2} = -2 \cdot \frac{1}{25} = -\frac{2}{25} matches our simplified fraction.

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