Simplify Base-7 Expression: 7^(2x+1) × 7^(-1) × 7^x

Exponent Rules with Multiple Base-7 Terms

72x+1717x= 7^{2x+1}\cdot7^{-1}\cdot7^x=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Simplify the following expression
00:02 When multiplying powers with the same base, add together the exponents
00:07 This formula applies to any number of bases
00:12 Let's apply this formula to our exercise
00:16 Let's add together all of the exponents
00:23 Combine the factors
00:34 This is the solution

Step-by-step written solution

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1

Understand the problem

72x+1717x= 7^{2x+1}\cdot7^{-1}\cdot7^x=

2

Step-by-step solution

We use the power property to multiply terms with identical bases:

aman=am+n a^m\cdot a^n=a^{m+n} We apply the property to our expression:

72x+1717x=72x+1+(1)+x=72x+11+x 7^{2x+1}\cdot7^{-1}\cdot7^x=7^{2x+1+(-1)+x}=7^{2x+1-1+x} We simplify the expression we got in the last step:

72x+11+x=73x 7^{2x+1-1+x}=7^{3x} When we add similar terms in the exponent.

Therefore, the correct answer is option d.

3

Final Answer

73x 7^{3x}

Key Points to Remember

Essential concepts to master this topic
  • Rule: When multiplying same bases, add their exponents: aman=am+n a^m \cdot a^n = a^{m+n}
  • Technique: Combine exponents step by step: (2x+1) + (-1) + x = 3x
  • Check: Verify by substituting x=1: 737171=73 7^3 \cdot 7^{-1} \cdot 7^1 = 7^3

Common Mistakes

Avoid these frequent errors
  • Multiplying the exponents instead of adding them
    Don't multiply exponents like (2x+1)(-1)(x) = -2x²-x! This confuses multiplication of powers with powers of powers. Always add exponents when multiplying terms with the same base.

Practice Quiz

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

FAQ

Everything you need to know about this question

Why do I add the exponents instead of multiplying them?

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The Product Rule for exponents states that aman=am+n a^m \cdot a^n = a^{m+n} . Think of it this way: 7273 7^2 \cdot 7^3 means (7×7) × (7×7×7) = 7×7×7×7×7 = 75 7^5 , which is 2+3!

What happens when I have a negative exponent like 7⁻¹?

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A negative exponent doesn't change the addition rule! Just treat -1 as a regular number when adding: (2x+1) + (-1) + x = 2x + 1 - 1 + x = 3x.

How do I handle the parentheses in (2x+1)?

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The parentheses show that the entire expression 2x+1 is the exponent. When adding exponents, treat (2x+1) as one unit: (2x+1) + (-1) + x.

Can I simplify this a different way?

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You could rearrange the terms first, like 72x+17x71 7^{2x+1} \cdot 7^x \cdot 7^{-1} , but you'll still get the same answer. The key is always adding all the exponents together!

What if the bases were different numbers?

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If you had something like 7x5x 7^x \cdot 5^x , you cannot combine them using this rule. The Product Rule only works when the bases are identical!

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