`a.` `y = (3x+1)/(2x-1) ` `(` ĐKXĐ : `x\ne 1/2``)`

`⇒y' = (3.(-1)-2.1)/((2x-1)^2)`

`⇒y'= (-5)/((2x-1)^2)`

`@` Công thức nhanh : `y=(ax+b)/(cx+d)⇒y'=(ad-bc)/(cx+d)^2`

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`b.` ` y = 2.sin(π/6-3x)`

`⇒y' = 2.(π/6-3x)' .cos(π/6-3x)`

`⇒y'= -6.cos(π/6-3x)`

`@ sin(u)=u' . cos(u)`