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# Stationary Points watch

1. I learned how to find stationary points with quadratic derivatives and stuff, but I came across this question and I'm really struggling to find the solution for this question.
Find the minimum point on the graph with equation y=√x+4/x, how do I find the stationarys?

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2. (Original post by cjayballs)
I learned how to find stationary points with quadratic derivatives and stuff, but I came across this question and I'm really struggling to find the solution for this question.
Find the minimum point on the graph with equation y=√x+4/x, how do I find the stationarys?
Same as how you usually do, just slightly trickier when dealing with hint negative indices hint.

It may help to divide each term by x to get rid of the denominator, assuming you have (a+b)/c there - what you have written is ambiguous!
3. Isn't that equation same as x^1/2 +4x^-1 differentiate it and make it equal zero
4. I can't tell if you mean [sqrt(x) + 4]/x or sqrt(x) + (4/x).
5. $f(x) = \sqrt x + \frac{4}{x}$
$f'(x) = -\frac{8-x^\frac{3}{2}}{2x^2}$
Factorise:

$-\frac{(2-x^\frac{1}{2})(x+4+2x^\frac{1}{2})}{2x}$

Let $f'(x) = 0$

$\implies x=4$

$\implies y = 3$

$\because \sqrt4 + \frac{4}{4} = 3$

Edit: probably wasn't wise giving the OP the full solution since it isn't beneficial... oops
6. But how do I rearrange the derivative in order to give me the stationary points when I have the derivative equal to 0?

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