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[tex]\displaystyle\bf\\2)\\\\\frac{x^{2}+25 }{(x-5)^{2} } -\frac{10x}{(5-x)^{2} } =\frac{x^{2}+25 }{(x-5)^{2} } -\frac{10x}{(x-5)^{2} } =\\\\\\=\frac{x^{2} -10x+25}{(x-5)^{2} } =\frac{(x-5)^{2} }{(x-5)^{2} } =1\\\\\\6)\\\\\frac{a}{2a-b} +\frac{3a-b}{b-2a} =\frac{a}{2a-b} -\frac{3a-b}{2a-b} =\\\\\\=\frac{a-3a+b}{2a-b} =\frac{-2a+b}{2a-b} =-\frac{2a-b}{2a-b} =-1[/tex]