# Thread:

1. ## stationary points question

"find the stationary points of the following curves and determine whether the points are maxima, minima, or points of inflexion"

y= (x + 1)/ (x - 1)

I know how to these sorts of questions but for this example i find it tricky, I set it as:

y= (x + 1) (x - 1)^-1 but then differentiating this is tricky - not sure how to use the chain rule on the latter, or the product rule overall.

thanks for any help.

2. Originally Posted by porge111
"find the stationary points of the following curves and determine whether the points are maxima, minima, or points of inflexion"

y= (x + 1)/ (x - 1)

I know how to these sorts of questions but for this example i find it tricky, I set it as:

y= (x + 1) (x - 1)^-1 but then differentiating this is tricky - not sure how to use the chain rule on the latter, or the product rule overall.

thanks for any help.
In this case I would use the quotient rule:

$f(x) = \dfrac{u(x)}{v(x)}~\implies~f'(x)=\dfrac{v(x) \cdot u'(x) - u(x) \cdot v'(x)}{(v(x))^2}$

You should come out with: $f'(x)=-\dfrac2{(x-1)^2}$
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