Bài 1:
\(a,=\dfrac{\left(x-y\right)\left(x+y\right)}{\left(x-y\right)\left(x+y+z\right)}=\dfrac{x+y}{x+y+z}\\ b,=\dfrac{\left(2x-y\right)\left(2x+y\right)\left(x-y\right)}{\left(2x+y\right)2x\left(x-y\right)}=\dfrac{2x-y}{2x}\)
Bài 2:
\(=\dfrac{2x}{x\left(x+2y\right)}+\dfrac{y}{y\left(x-2y\right)}+\dfrac{4}{\left(x-2y\right)\left(x+2y\right)}\\ =\dfrac{2x^2y-4xy^2+x^2y+2xy^2+4xy}{xy\left(x+2y\right)\left(x-2y\right)}=\dfrac{3x^2y-2xy^2+4xy}{xy\left(x+2y\right)\left(x-2y\right)}\\ =\dfrac{3x-2y+4}{\left(x-2y\right)\left(x+2y\right)}\)
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