[tex]f(x)= \frac{1}{x} \\ \\ (3,f(3))=(3,\frac{1}{3} ) \\ \\ (3+h,f(3+h))=(3+h,\frac{1}{3+h} ) \\ \\ m= \frac{\frac{1}{3+h}-\frac{1}{3}}{3+h-3} =\frac{ \frac{3-(3+h)}{3(3+h)}}{h} =\frac{ 3-3-h}{3(3+h)h} = \frac{-h}{3(3+h)h} =- \frac{1}{3(3+h)}
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