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Find and justify the inflection point.

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

TOPIC 01

2022 JM02

The concavity check distinguishes an inflection from a mere zero of f″.

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

01 / Standard#Your turn

Find and justify the inflection point.

f(x)=x3−3x2+2f(x)=x^3-3x^2+2

Official paper · jm02-2022 · 2(a)(iv) · PDF 4

Official original and suggested answers ↗ · Suggested answer PDF page 9

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1
Set 6x−6=0.
Hint 2
Verify a change in sign, then calculate f.
Worked solution
  1. The second derivative changes from negative to positive at x=1.

    f′′(x)=6(x−1)f''(x)=6(x-1)
  2. The given zero supplies its ordinate.

    f(1)=0  ⟹  (1,0)f(1)=0\implies(1,0)

Inflection point (1,0).

Checks and common pitfalls: The concavity check distinguishes an inflection from a mere zero of f″.

Reasoning checklist · self / teacher assessment
  • Teaching assessment checklist, independently authored. Use the original paper for official marks.
  • The second derivative changes from negative to positive at x=1.
    f′′(x)=6(x−1)f''(x)=6(x-1)
  • The given zero supplies its ordinate.
    f(1)=0  ⟹  (1,0)f(1)=0\implies(1,0)

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Curriculum and source notes ↗