TMUA-P2-ERR1-002 — Paper P2 · Identifying errors in proofs · Level 1

Options

1. A
   Line (1): $(-4)^2 \ne 16$.
2. B
   Line (2): $\sqrt{16} \ne 4$.
3. C
   The cited rule is false for $x < 0$: in fact $\sqrt{x^2} = |x|$, so lines (1)–(2) give $4$, and line (3) contradicts them.
4. D
   Line (3) is valid and the earlier lines are wrong.
5. E
   No error exists; $\sqrt{(-4)^2} = -4$.

Letters only — the answer key is hidden. Work it out, then check the solution below.

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