9(x-y)²-12(y²-x²)+4(x+y)²
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9(x-y)²-12(y²-x²)+4(x+y)²9(x-y)²-12(y²-x²)+4(x+y)²9(x-y)
9(x-y)²-12(y²-x²)+4(x+y)²
9(x-y)²-12(y²-x²)+4(x+y)²
9(x-y)²-12(y²-x²)+4(x+y)²
9(x-y)²-12(y²-x²)+4(x+y)²
=[3(x-y)]²+2·[3(x-y)]·[2(x+y)]+[2(x+y)]²
=[3(x-y)+2(x+y)]²
=(5x-y)².