[tex]\bf f(x)=\cfrac{sin(x)}{x^2}\implies \cfrac{dy}{dx}=\cfrac{x^2cos(x)-2xsin(x)}{(x^2)^2}
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\cfrac{dy}{dx}=\cfrac{x[xcos(x)-2sin(x)]}{x^4}\implies \cfrac{dy}{dx}=\cfrac{xcos(x)-2sin(x)}{x^3}
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-----------------------------\\\\[/tex]
[tex]\bf f(x)=(3x^2+2x-1)^4\implies \cfrac{dy}{dx}=4(3x^2+2x-1)^3(6x+2)
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f(x)=\left( \cfrac{x-5}{2x+1} \right)^2\implies \cfrac{dy}{dx}=2\left( \cfrac{x-5}{2x+1} \right)\left[ \cfrac{2x+1-2(x-5)}{(2x-1)^2} \right]
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\cfrac{dy}{dx}=2\left( \cfrac{x-5}{2x+1} \right)\left[ \cfrac{11}{(2x-1)^2} \right][/tex]
