Solve the Expression: Finding 7^1 - 7^2

Exponent Evaluation with Negative Results

Solve the following exercise and circle the correct answer:

7172= 7^1-7^2=

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solve the following expression
00:04 Break down the exponents
00:12 Always solve multiplication and division before addition and subtraction
00:19 Continue to solve the expression according to the correct order of operations, from left to right
00:23 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 exercise and circle the correct answer:

7172= 7^1-7^2=

2

Step-by-step solution

To solve the expression 7172 7^1 - 7^2 , we need to evaluate the powers first before performing the subtraction. The steps are as follows:

  • Calculate 71 7^1 : Since any number to the power of 1 is the number itself, we have 71=7 7^1 = 7 .
  • Calculate 72 7^2 : This means 7 is multiplied by itself, which gives us 7×7=49 7 \times 7 = 49 .
  • Subtract the results: Now, perform the subtraction 749 7 - 49 .
  • This yields: 749=42 7 - 49 = -42 .

Thus, the correct answer is 42 -42 .

3

Final Answer

42 -42

Key Points to Remember

Essential concepts to master this topic
  • Rule: Always calculate exponents before performing subtraction operations
  • Technique: Evaluate 71=7 7^1 = 7 and 72=49 7^2 = 49 first
  • Check: Substitute back: 749=42 7 - 49 = -42 matches our answer ✓

Common Mistakes

Avoid these frequent errors
  • Performing subtraction before evaluating exponents
    Don't subtract the exponents like 7^(1-2) = 7^(-1) = 1/7! This ignores order of operations and gives a completely wrong result. Always evaluate each exponent first, then perform the subtraction operation.

Practice Quiz

Test your knowledge with interactive questions

\( 11^2= \)

FAQ

Everything you need to know about this question

Why is the answer negative when both numbers are positive?

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Great question! Even though 7 is positive, we're subtracting a larger number (49) from a smaller one (7). Whenever you subtract a larger number from a smaller one, the result is negative: 749=42 7 - 49 = -42 .

Do I need to follow order of operations here?

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Yes, absolutely! Remember PEMDAS: Parentheses, Exponents, Multiplication/Division, Addition/Subtraction. Since exponents come before subtraction, calculate 71 7^1 and 72 7^2 first, then subtract.

What does 7^1 equal and why?

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Any number raised to the power of 1 equals itself. So 71=7 7^1 = 7 . This is because you're multiplying the base by itself 1 time, which is just the number itself!

How do I calculate 7^2 without a calculator?

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72 7^2 means 7 × 7. You can break it down: 7×7=(5+2)×7=35+14=49 7 \times 7 = (5 + 2) \times 7 = 35 + 14 = 49 . Practice your multiplication tables to make this faster!

Could the answer be positive instead?

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No, the answer must be negative. Since we're calculating 749 7 - 49 , we're subtracting 49 from 7. This always gives -42, not +42. The order matters in subtraction!

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