The following calculation is correct: A: 3Y / X △ 3xy = x ^ 2 B: 3Y / x ^ 2 △ X / 3Y = 1 / X C: X △ y * 1 / y = x D: A / A ^ 2-1 * A-1 / a = 1 / A + 1

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A exclude first: 3Y and 3Y go together, leaving 1 / x ^ 2
,B:9Y^2/X^3C:x/y^2
C:X/Y^2
D: (a ^ 2-1) is equal to (a + 1) (A-1), A-1 is reduced, a is reduced, and 1 / (a + 1) is obtained
Choose D

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