LEARN · EXPLAIN · REVISE

Solve the power comparison for positive x.

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

高一必修第一册(A版).pdf · 3.3 · PDF 96 / printed page 89

TOPIC 01

Power functions

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

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

01 / Standard#Your turn

x^{-1}>3

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Identify the exponent, its real domain and how it changes order.

Hint 2

Multiply by x only after noting x>0.

Worked solution

0<x<1/3.

Checks and common pitfalls: A reciprocal power decreases on the positive half-line.

Reasoning checklist · self / teacher assessment

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

Teacher preparation and assessment

Interpret and use power functions with domain checks.
Fixed exponent: A power function has the form x to a fixed exponent with its real domain.
$y=x^a$
Domains and order: Negative, fractional and integer exponents have different restrictions and behaviours.
Close with: conditions → representation → reasoning → check.

Expected reasoning: A power function has the form x to a fixed exponent with its real domain.
Expected reasoning: Negative, fractional and integer exponents have different restrictions and behaviours.
Expected correction: A negative exponent does not mean a negative output.