[tex]zad.a\\
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y=\dfrac{5x-15}{9x^{2} -81} =\dfrac{5x-15}{(3x)^{2} -9^{2} } =\dfrac{5x-15}{(3x-9)\cdot (3x+9)} \\
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D_{y} =R- \{ -3,3\}\\
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5x-15=0\\
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5x=15~~\mid \div 5\\
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x=3~~\land x\in D_{y} ~~\Rightarrow~~x\not\in D_{y} ~~\Rightarrow ~~brak~~miejsc ~~zerowych[/tex]
[tex]zad.b\\
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y=\sqrt{6x-14} \\
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zal.\\
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6x-14\geq 0\\
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6x\geq 14~~\mid \div 6\\
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x \geq 2\frac{1}{3} \\
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D_{y} =<2\frac{1}{3} ,+\infty )\\
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\sqrt{6x-14}=0~~\mid ()^{2} \\
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6x-14=0\\
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6x=14~~\mid \div 6\\
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x=2\frac{1}{3} ~~\land ~~D_{y} =<2\frac{1}{3} ,+\infty )~~\Rightarrow ~~x=2\frac{1}{3} [/tex]
[tex]zad.c\\
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y=2x^{2} +7\\
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D_{y} =R\\
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2x^{2} +7=0\\
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2x^{2} =-7~~\mid \div 2\\
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x^{2} =-3\frac{1}{2} ~~\Rightarrow ~~x\in \not 0~~\Rightarrow ~~brak ~~miejsc ~~zerowych [/tex]
