Competition problem — Algebra — Maths Olympiad Prep

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Algebra Difficulty 1.8 Junior Find the answer

If $x = 2y$ and $y \neq 0$ , what is the value of $(x-y)(2x+y)$ ?

Your answer

A number or a short expression. Spacing and $ signs are ignored.

Solution

Since $x = 2y$ , then $(x-y)(2x+y) = (2y-y)(2(2y)+y) = (y)(5y) = 5y^{2}$ .

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