Level 3 Differentiation Walkthrough

2022 NCEA Level 3 Differentiation Question 3(b)

2022 Paper - Reading differentiability and limits from a graph

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Question

The graph below shows the function \(y=f(x)\).

-6 -5 -4 -3 -2 -1 1 2 3 4 -5 -4 -3 -2 -1 1 2 3 4 5 x y
\[ \text{(i) Find the value(s) of } x \text{ where } f(x) \text{ is not differentiable.} \] \[ \text{(ii) Find the value(s) of } x \text{ for which } f'(x)=0. \] \[ \text{(iii) What is the value of } \lim_{x\to -4} f(x)\text{?} \]

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First walkthrough idea

Tip to try first

Non-differentiable points often appear where the graph has a hole or a sharp corner.

Step 1

Locate the non-differentiable x-values

Reveal the explanation and working for this step.

Show the first step’s working

Look for holes, sharp corners, or jumps.

Key result

\[ x=-4,\,-1,\text{ and }1 \]

There is a hole at \(x=-4\), a corner at \(x=-1\), and another corner where the sloping segment meets the horizontal ray at \(x=1\).

Walkthrough overview

What this question practises

This 2022 walkthrough is part of AS91578 — Apply differentiation methods in solving problems.

Method: Reading differentiability, derivatives, and limits from a graph.

This is Question 3(b) from the 2022 NCEA Level 3 Differentiation paper for AS91578 — Apply differentiation methods in solving problems. Use the guided hints to practise the method before revealing the full working.

Calc.nz is an independent learning resource. Compare questions, diagrams, and assessment information with the official NZQA resources for AS91578.

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Learning summary

Review the method, not only the answer

This walkthrough helps you practise reading differentiability, derivatives, and limits from a graph. Use the hints to plan the method, then repeat the question without hints and check each step.

Common mistake to avoid

Check each step against the original condition, preserve signs and restrictions, and confirm that the final result answers the question asked.

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