2023 AMC 12A Problem 10

Below is the professionally curated solution for Problem 10 of the 2023 AMC 12A, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2023 AMC 12A solutions, or check the answer key.

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Concepts:system of equationssubstitution

Difficulty rating: 1560

10.

Positive real numbers xx and yy satisfy y3=x2y^3=x^2 and (yx)2=4y2.(y-x)^2=4y^2. What is x+y?x+y?

1212

1818

2424

3636

4242

Solution:

From (yx)2=4y2(y-x)^2=4y^2 we get yx=±2y.y-x=\pm 2y. The choice yx=2yy-x=2y gives x=y<0,x=-y\lt 0, impossible, so yx=2y,y-x=-2y, meaning x=3y.x=3y.

Substituting into y3=x2=9y2y^3=x^2=9y^2 gives y=9,y=9, hence x=27x=27 and x+y=36.x+y=36.

Thus, the correct answer is D.

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