Simplify the Expression: 7^5 × 7^(-6) Using Laws of Exponents

Exponent Rules with Negative Powers

7576=? 7^5\cdot7^{-6}=\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 (M)
00:05 multiplied by the same number (A) raised to the power of (N)
00:08 equals the number (A) raised to the power of (M+N)
00:11 Let's apply this to the problem
00:14 We obtain the number (7) raised to the power of (5+(-6))
00:17 Let's calculate this power
00:20 According to the laws of exponents, any number (A) raised to the power of (-N)
00:23 equals 1 divided by the number (A) raised to the power of (N)
00:26 Let's apply this to the problem
00:29 We obtain 1 divided by (7) raised to the power of (1)
00:32 This is the solution

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

7576=? 7^5\cdot7^{-6}=\text{?}

2

Step-by-step solution

We begin by using the rule for multiplying exponents. (the multiplication between terms with identical bases):

aman=am+n a^m\cdot a^n=a^{m+n} We then apply it to the problem:

7576=75+(6)=756=71 7^5\cdot7^{-6}=7^{5+(-6)}=7^{5-6}=7^{-1} When in a first stage we begin by applying the aforementioned rule and then continue on to simplify the expression in the exponent,

Next, we use the negative exponent rule:

an=1an a^{-n}=\frac{1}{a^n} We apply it to the expression obtained in the previous step:

71=171=17 7^{-1}=\frac{1}{7^1}=\frac{1}{7} We then summarise the solution to the problem: 7576=71=17 7^5\cdot7^{-6}=7^{-1}=\frac{1}{7} Therefore, the correct answer is option B.

3

Final Answer

17 \frac{1}{7}

Key Points to Remember

Essential concepts to master this topic
  • Product Rule: When multiplying same bases, add the exponents: aman=am+n a^m \cdot a^n = a^{m+n}
  • Technique: 7576=75+(6)=71 7^5 \cdot 7^{-6} = 7^{5+(-6)} = 7^{-1} by adding exponents
  • Check: Convert negative exponent: 71=171=17 7^{-1} = \frac{1}{7^1} = \frac{1}{7}

Common Mistakes

Avoid these frequent errors
  • Subtracting exponents instead of adding them
    Don't calculate 7576 7^5 \cdot 7^{-6} as 756 7^{5-6} directly = skipping the addition step! The product rule says to add exponents, so 5 + (-6) = 5 - 6 = -1. Always write out the addition first: 75+(6) 7^{5+(-6)} , then simplify.

Practice Quiz

Test your knowledge with interactive questions

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

FAQ

Everything you need to know about this question

Why do I add the exponents when multiplying?

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The product rule for exponents states that aman=am+n a^m \cdot a^n = a^{m+n} . This works because you're essentially multiplying the base by itself multiple times. For example, 7273=(77)(777)=75 7^2 \cdot 7^3 = (7 \cdot 7) \cdot (7 \cdot 7 \cdot 7) = 7^5 .

What does a negative exponent mean?

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A negative exponent means take the reciprocal and make the exponent positive. So 71=171=17 7^{-1} = \frac{1}{7^1} = \frac{1}{7} . Think of it as 'flipping' the number to the denominator.

Can I just subtract 6 from 5 directly?

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Yes, but be careful with the signs! Since we have 7576 7^5 \cdot 7^{-6} , we add the exponents: 5 + (-6) = 5 - 6 = -1. The key is recognizing that adding a negative number is the same as subtraction.

How do I know when to use the product rule?

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Use the product rule whenever you're multiplying terms with the same base. Look for expressions like aman a^m \cdot a^n . If the bases are different (like 7234 7^2 \cdot 3^4 ), you cannot use this rule.

What if I get confused about negative exponents?

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Remember the simple rule: an=1an a^{-n} = \frac{1}{a^n} . A negative exponent always creates a fraction with 1 in the numerator. Practice with small numbers first, like 21=12 2^{-1} = \frac{1}{2} .

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