S
satthucaonguyen


a) [TEX](x-y+4)^2-(2x+3y-1)^2 [/TEX]
b) [TEX]9x^2+90x+225-(x-7)^2 [/TEX]
c) [TEX]49(y-4)^2-9y^2-36y-36[/TEX]
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~~Chú ý thanh TEX để gõ công thức nhé bạn
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