(x + y)(x - y) = y (x - y)If we substitute the values of x and y we have

(2)(0) = (1)(0)or

0 = 0However, when we divide both sides by (x - y), we break a fundamental rule of mathematics that we cannot divide out by a fraction which is equal to zero.

Source: Longley-Cook, L. H.

Categories: Reasoning, Algebra, Pitfall, Favorite

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