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tmua.fyi Paper 2 Challenge 2 · Q6

Paper 2Algebra

The following argument is offered, where aa and bb are non-zero real numbers.

(1)a=b(2)a2=ab(3)a2−b2=ab−b2(4)(a−b)(a+b)=b(a−b)(5)a+b=b(6)2b=b, so 2=1\begin{aligned} (1)\quad&a=b\\ (2)\quad&a^2=ab\\ (3)\quad&a^2-b^2=ab-b^2\\ (4)\quad&(a-b)(a+b)=b(a-b)\\ (5)\quad&a+b=b\\ (6)\quad&2b=b,\text{ so }2=1 \end{aligned}

At which step does the argument first fail?

Astep (2)
Bstep (3)
Cstep (4)
Dstep (5)
Estep (6)
Fstep (1)
Gmore than one step fails
Hit does not fail

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