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Compare the powers without decimal approximations.

Read the idea, work independently, then explain what changed.

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高一必修 第一册(A版).pdf · 4.1 · PDF 111 / printed page 104

Revisit first: Applications of functions I

TOPIC 01

Exponents

Build understanding of exponents through definitions, contrasting cases and justified applications.

What you will be able to explain

  • Interpret and use exponents with domain checks.
  • Connect representations and justify the steps, including boundary cases.
  • Explain a solution and apply the idea to a changed situation.

Try it. Leave your reasoning visible.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Standard#Your turn

Compare the powers without decimal approximations.

(1/3)2,(1/3)3(1/3)^2,\quad(1/3)^3
  • Use the domain, units and sampling assumptions stated in the question.
Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1
Use exponent laws only within their real-number domain.
Hint 2
The common base is between zero and one.
Worked solution
  1. Use exponent laws only within their real-number domain.

  2. Calculate or simplify this relation.

    (1/3)2−(1/3)3=(3−1)/27>0(1/3)^2-(1/3)^3=(3-1)/27>0
  3. Increasing a positive exponent reduces a power with base between zero and one.

The squared value is larger.

Checks and common pitfalls: Increasing a positive exponent reduces a power with base between zero and one.

Reasoning checklist · self / teacher assessment
  • State the relevant definition, condition or model.
  • Show a valid calculation, proof or counterexample.
  • Interpret the conclusion with its restrictions.

Think first. Reveal a hint when the class is ready.

Focus on one question

Teacher preparation and assessment

Question sequence

  • What must be true before using the main rule for exponents?
  • Which representation makes this task easier, and why?
  • Change one assumption. Does the conclusion survive?

Board plan

  • Interpret and use exponents with domain checks.
  • Exponent laws: Use common-base product and quotient laws within their valid domains.
    aman=am+na^ma^n=a^{m+n}
  • Roots: Principal even roots are nonnegative; odd roots allow negative arguments.
  • Close with: conditions → representation → reasoning → check.

Anticipated thinking

  • Expected reasoning: Use common-base product and quotient laws within their valid domains.
  • Expected reasoning: Principal even roots are nonnegative; odd roots allow negative arguments.
  • Expected correction: The square root of x² is |x|, not always x.

Assessment checklist

  • 1: identify the givens and required quantity.
  • 1: choose a valid definition, representation or method.
  • 1: present connected, correct reasoning.
  • 1: check conditions and explain the result.

No sign-in. Work stays in this browser. Export before clearing browser data. Written reasoning is assessed with a checklist.

Curriculum and source notes ↗