JUPEBMathematicsDifferentiation

Find $\dfrac{dy}{dx}$ if $y = \dfrac{2x + 1}{x - 1}$.

A$\dfrac{3}{(x - 1)^2}$
B$\dfrac{2}{(x - 1)^2}$
C$\dfrac{4x - 1}{(x - 1)^2}$
D$\dfrac{-3}{(x - 1)^2}$CORRECT
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Why the answer is D, and why the others tempt you.
Use the quotient rule $\dfrac{u'v - uv'}{v^2}$ with $u = 2x + 1$ and $v = x - 1$: numerator $2(x - 1) - (2x + 1)(1) = 2x - 2 - 2x - 1 = -3$, so $\dfrac{dy}{dx} = \dfrac{-3}{(x-1)^2}$. Reversing the order of the two terms in the numerator gives $+3$.
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