LEARN · EXPLAIN · REVISE

Find the coefficient of x² in (1+x)^m.

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

TOPIC 01

Counting principles: mixed review

A mixed assessment: identify the method, justify it and revise your reasoning.

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

01 / Foundation#Your turn

m=7

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Decide whether choices are alternative cases or successive stages, then check overlap.

Hint 2

Use this intermediate relation.

C_m^2=m(m-1)/2

Worked solution

Decide whether choices are alternative cases or successive stages, then check overlap.
Apply the stated relation and retain its conditions.
$[x^2]=21$
The unordered pair of chosen factors determines the term.

The requested value is 21.

Checks and common pitfalls: The unordered pair of chosen factors determines the term.

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

Teacher preparation and assessment