# Help : Proof that 2 = 1

Let $$a$$ and $$b$$ are two numbers such that $$a = b = 2$$.

Therefore $$a^2 = ab$$ [multiplying $$a$$ on both sides.]

$$a^2 - b^2 = ab - b^2$$ [subtracting $$b^2$$ on both sides.]

$$(a + b)(a - b) = b(a-b)$$

$$(a+b) = b$$

Now substituting the values of $$a$$ and $$b$$ , we get $$2+2 = 2$$

Therefore $$4 = 2$$ ?

Note by Rama Devi
2 years, 11 months ago

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you cannot cancel (a-b) on both sides because (a-b) =0 and division by 0 is not defined!

- 2 years, 11 months ago

good observation

- 2 years, 11 months ago

You are only 13 and you are level 5 in all subjects .Cool! Do you sit whole day at brilliant or you attempt every question correctly?

- 2 years, 11 months ago

You cannot cancel out (a-b). Think why?

Staff - 2 years, 11 months ago

Because a - b is 0

- 2 years, 11 months ago