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\(a,=\sqrt{xy}\left(\sqrt{x}-1\right)+\left(\sqrt{x}-1\right)=\left(\sqrt{xy}+1\right)\left(\sqrt{x}-1\right)\\ b,=\sqrt{xy}\left(\sqrt{x}+1\right)+\left(\sqrt{x}+1\right)=\left(\sqrt{x}+1\right)\left(\sqrt{xy}+1\right)\)
\(x\sqrt{x}+x-y+y\sqrt{x}-xy\sqrt{x}-xy\sqrt{y}=\left(x\sqrt{y}+y\sqrt{x}\right)+\left(x-y\right)-\left(xy\sqrt{x}+xy\sqrt{y}\right)\)
\(=\sqrt{xy}\left(\sqrt{x}+\sqrt{y}\right)+\left(\sqrt{x}+\sqrt{y}\right)\left(\sqrt{x}-\sqrt{y}\right)-xy\left(\sqrt{x}+\sqrt{y}\right)\)
\(=\left(\sqrt{x}+\sqrt{y}\right)\left(\sqrt{xy}+\sqrt{x}-\sqrt{y}-xy\right)\)
a) \(=9x-9\sqrt{xy}+4\sqrt{xy}-4y\)
\(=\left(9x-9\sqrt{xy}\right)+\left(4\sqrt{xy}-4y\right)\)
\(=9\sqrt{x}\left(\sqrt{x}-\sqrt{y}\right)+4\sqrt{y}\left(\sqrt{x}-\sqrt{y}\right)\)
\(=\left(\sqrt{x}-\sqrt{y}\right)\left(9\sqrt{x}+4\sqrt{y}\right)\)
b)\(=\left(xy+\sqrt{x}.y\right)+\left(\sqrt{x}+1\right)\)
\(=\sqrt{x}y\left(\sqrt{x}+1\right)+\left(\sqrt{x}+1\right)\)
\(=\left(\sqrt{x}+1\right)\left(\sqrt{x}.y+1\right)\)
\(Sửa:x+y-9-2\sqrt{xy}\\ =\left(\sqrt{x}-\sqrt{y}\right)^2-9=\left(\sqrt{x}-\sqrt{y}-3\right)\left(\sqrt{x}-\sqrt{y}+3\right)\)
\(\sqrt{xy}+1+\sqrt{x}+\sqrt{y}\)
=\(\sqrt{x}\left(\sqrt{y}+1\right)+\left(\sqrt{y}+1\right)\)
\(=\left(\sqrt{y}+1\right)\left(\sqrt{x}+1\right)\)
\(xy-y\sqrt{x}+\sqrt{x}-1\)
\(=y\left(x-\sqrt{x}\right)+\left(\sqrt{x}-1\right)\)
\(=y\sqrt{x}\left(\sqrt{x}-1\right)+\left(\sqrt{x}-1\right)\)
\(\left(\sqrt{x}-1\right)\left(y\sqrt{x}+1\right)\)
a: \(A=x\sqrt{x}-y\sqrt{y}+x\sqrt{y}-y\sqrt{x}\)
\(=\left(\sqrt{x}-\sqrt{y}\right)\left(x+\sqrt{xy}+y\right)+\sqrt{xy}\left(\sqrt{x}-\sqrt{y}\right)\)
\(=\left(\sqrt{x}-\sqrt{y}\right)\left(\sqrt{x}+\sqrt{y}\right)^2\)
b: \(B=5x^2-7x\sqrt{y}+2y\)
\(=5x^2-5x\sqrt{y}-2x\sqrt{y}+2y\)
\(=5x\left(x-\sqrt{y}\right)-2\sqrt{y}\left(x-\sqrt{y}\right)\)
\(=\left(x-\sqrt{y}\right)\left(5x-2\sqrt{y}\right)\)
\(B=\left(3\sqrt{x}\right)^2+2.3\sqrt{x}.\sqrt{y}+\sqrt{y}^2=\left(3\sqrt{x}+\sqrt{y}\right)^2\)
Hằng đẳng thức dễ mà bạn: a^2 + 2ab + b^2 = (a+b)^2
Còn điều kiện s b?