tmua.fyi Mock Paper 2 · Question 7

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tmua.fyi Mock Paper 2 · Q7

Paper 2Algebra

The following argument claims to show that every real number equals $0$ .

Line 1: Let $a=b$ .

Line 2: Then $a^2=ab$ .

Line 3: So $a^2-b^2=ab-b^2$ .

Line 4: Factorising, $(a-b)(a+b)=b(a-b)$ .

Line 5: Dividing by $a-b$ , $a+b=b$ .

Line 6: Hence $a=0$ .

At which line does the first error occur?

ALine 2

BLine 3

CLine 4

DLine 5

ELine 6

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