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x-(9/x)
Plotting a function graph/ x-(9/x)

Graphing y = x-(9/x)

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The graph:

from to

Intersection points:

does show?

Piecewise:

The solution

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           9
f(x) = x - -
           x
f(x)=x−9xf{\left(x \right)} = x - \frac{9}{x} 
f = x - 9/x
The graph of the function
02468-8-6-4-2-1010-500500
The domain of the function
The points at which the function is not precisely defined:
x1=0x_{1} = 0
The points of intersection with the X-axis coordinate
Graph of the function intersects the axis X at f = 0
so we need to solve the equation:
x−9x=0x - \frac{9}{x} = 0
Solve this equation
The points of intersection with the axis X:

Analytical solution
x1=−3x_{1} = -3
x2=3x_{2} = 3
Numerical solution
x1=3x_{1} = 3
x2=−3x_{2} = -3
The points of intersection with the Y axis coordinate
The graph crosses Y axis when x equals 0:
substitute x = 0 to x - 9/x.
0−900 - \frac{9}{0}
The result:
f(0)=∞~f{\left(0 \right)} = \tilde{\infty}
sof doesn't intersect Y
Extrema of the function
In order to find the extrema, we need to solve the equation
ddxf(x)=0\frac{d}{d x} f{\left(x \right)} = 0
(the derivative equals zero),
and the roots of this equation are the extrema of this function:
ddxf(x)=\frac{d}{d x} f{\left(x \right)} =
the first derivative
1+9x2=01 + \frac{9}{x^{2}} = 0
Solve this equation
Solutions are not found,
function may have no extrema
Inflection points
Let's find the inflection points, we'll need to solve the equation for this
d2dx2f(x)=0\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
d2dx2f(x)=\frac{d^{2}}{d x^{2}} f{\left(x \right)} =
the second derivative
−18x3=0- \frac{18}{x^{3}} = 0
Solve this equation
Solutions are not found,
maybe, the function has no inflections
Vertical asymptotes
Have:
x1=0x_{1} = 0
Horizontal asymptotes
Let’s find horizontal asymptotes with help of the limits of this function at x->+oo and x->-oo
lim⁡x→−∞(x−9x)=−∞\lim_{x \to -\infty}\left(x - \frac{9}{x}\right) = -\infty
Let's take the limit
so,
horizontal asymptote on the left doesn’t exist
lim⁡x→∞(x−9x)=∞\lim_{x \to \infty}\left(x - \frac{9}{x}\right) = \infty
Let's take the limit
so,
horizontal asymptote on the right doesn’t exist
Inclined asymptotes
Inclined asymptote can be found by calculating the limit of x - 9/x, divided by x at x->+oo and x ->-oo
lim⁡x→−∞(x−9xx)=1\lim_{x \to -\infty}\left(\frac{x - \frac{9}{x}}{x}\right) = 1
Let's take the limit
so,
inclined asymptote equation on the left:
y=xy = x
lim⁡x→∞(x−9xx)=1\lim_{x \to \infty}\left(\frac{x - \frac{9}{x}}{x}\right) = 1
Let's take the limit
so,
inclined asymptote equation on the right:
y=xy = x
Even and odd functions
Let's check, whether the function even or odd by using relations f = f(-x) и f = -f(-x).
So, check:
x−9x=−x+9xx - \frac{9}{x} = - x + \frac{9}{x}
- No
x−9x=x−9xx - \frac{9}{x} = x - \frac{9}{x}
- No
so, the function
not is
neither even, nor odd
The graph
Graphing y = x-(9/x)
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