Maths Olympiad Prep

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Problem 858

AMC 12 late, AIME early
Algebra Difficulty 4.6 Find the answer HMMT February

The graph of x4=x2y2x^{4}=x^{2} y^{2} is a union of nn different lines. What is the value of nn?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

The equation x4x2y2=0x^{4}-x^{2} y^{2}=0 factors as x2(x+y)(xy)=0x^{2}(x+y)(x-y)=0, so its graph is the union of the three lines x=0,x+y=0x=0, x+y=0, and xy=0x-y=0.

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