Rút gọn \(\frac{x^2}{x+y} + \frac{y^2}{y+z} + \frac{-y^2}{x+y} + \frac{-z^2}{y+z};\)

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y) \(\frac{x^2}{x+y} + \frac{y^2}{y+z} + \frac{-y^2}{x+y} + \frac{-z^2}{y+z};\)

J) \(A = \frac{20x^2 + 120x + 180}{(3x + 5)^2 - 4x^2} + \frac{5x^2 - 125}{9x^2 - (2x + 5)^2} - \frac{(2x + 3)^2 - x^2}{3x^2 + 8x + 15}.\)