Mister Exam

Graphing y = (x+ln(x))/(x-4)

v

The graph:

from to

Intersection points:

does show?

Piecewise:

The solution

You have entered [src]
       x + log(x)
f(x) = ----------
         x - 4   
f(x)=x+log(x)x4f{\left(x \right)} = \frac{x + \log{\left(x \right)}}{x - 4}
f = (x + log(x))/(x - 4)
The graph of the function
02468-8-6-4-2-1010-250250
The domain of the function
The points at which the function is not precisely defined:
x1=4x_{1} = 4
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+log(x)x4=0\frac{x + \log{\left(x \right)}}{x - 4} = 0
Solve this equation
The points of intersection with the axis X:

Analytical solution
x1=W(1)x_{1} = W\left(1\right)
Numerical solution
x1=0.567143290409784x_{1} = 0.567143290409784
The points of intersection with the Y axis coordinate
The graph crosses Y axis when x equals 0:
substitute x = 0 to (x + log(x))/(x - 4).
log(0)4\frac{\log{\left(0 \right)}}{-4}
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+1xx4x+log(x)(x4)2=0\frac{1 + \frac{1}{x}}{x - 4} - \frac{x + \log{\left(x \right)}}{\left(x - 4\right)^{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
2(1+1x)x4+2(x+log(x))(x4)21x2x4=0\frac{- \frac{2 \left(1 + \frac{1}{x}\right)}{x - 4} + \frac{2 \left(x + \log{\left(x \right)}\right)}{\left(x - 4\right)^{2}} - \frac{1}{x^{2}}}{x - 4} = 0
Solve this equation
The roots of this equation
x1=38783.8985529685x_{1} = 38783.8985529685
x2=45808.020325951x_{2} = 45808.020325951
x3=29719.8418978506x_{3} = 29719.8418978506
x4=37778.7731403642x_{4} = 37778.7731403642
x5=31737.8127530236x_{5} = 31737.8127530236
x6=40792.827428034x_{6} = 40792.827428034
x7=30729.1207207176x_{7} = 30729.1207207176
x8=0.8114375561742x_{8} = 0.8114375561742
x9=47811.4762989485x_{9} = 47811.4762989485
x10=46809.925612916x_{10} = 46809.925612916
x11=34760.5793720106x_{11} = 34760.5793720106
x12=28709.9529706705x_{12} = 28709.9529706705
x13=35767.1290742184x_{13} = 35767.1290742184
x14=48812.6813980915x_{14} = 48812.6813980915
x15=44805.7509925326x_{15} = 44805.7509925326
x16=42800.0800645983x_{16} = 42800.0800645983
x17=43803.1077057361x_{17} = 43803.1077057361
x18=41796.6571384727x_{18} = 41796.6571384727
x19=32745.9397987124x_{19} = 32745.9397987124
x20=36773.1883391132x_{20} = 36773.1883391132
x21=27699.4289684316x_{21} = 27699.4289684316
x22=33753.5222833995x_{22} = 33753.5222833995
x23=39788.5788225481x_{23} = 39788.5788225481
You also need to calculate the limits of y '' for arguments seeking to indeterminate points of a function:
Points where there is an indetermination:
x1=4x_{1} = 4

limx4(2(1+1x)x4+2(x+log(x))(x4)21x2x4)=\lim_{x \to 4^-}\left(\frac{- \frac{2 \left(1 + \frac{1}{x}\right)}{x - 4} + \frac{2 \left(x + \log{\left(x \right)}\right)}{\left(x - 4\right)^{2}} - \frac{1}{x^{2}}}{x - 4}\right) = -\infty
limx4+(2(1+1x)x4+2(x+log(x))(x4)21x2x4)=\lim_{x \to 4^+}\left(\frac{- \frac{2 \left(1 + \frac{1}{x}\right)}{x - 4} + \frac{2 \left(x + \log{\left(x \right)}\right)}{\left(x - 4\right)^{2}} - \frac{1}{x^{2}}}{x - 4}\right) = \infty
- the limits are not equal, so
x1=4x_{1} = 4
- is an inflection point

Сonvexity and concavity intervals:
Let’s find the intervals where the function is convex or concave, for this look at the behaviour of the function at the inflection points:
Concave at the intervals
(,0.8114375561742]\left(-\infty, 0.8114375561742\right]
Convex at the intervals
[0.8114375561742,)\left[0.8114375561742, \infty\right)
Vertical asymptotes
Have:
x1=4x_{1} = 4
Horizontal asymptotes
Let’s find horizontal asymptotes with help of the limits of this function at x->+oo and x->-oo
limx(x+log(x)x4)=1\lim_{x \to -\infty}\left(\frac{x + \log{\left(x \right)}}{x - 4}\right) = 1
Let's take the limit
so,
equation of the horizontal asymptote on the left:
y=1y = 1
limx(x+log(x)x4)=1\lim_{x \to \infty}\left(\frac{x + \log{\left(x \right)}}{x - 4}\right) = 1
Let's take the limit
so,
equation of the horizontal asymptote on the right:
y=1y = 1
Inclined asymptotes
Inclined asymptote can be found by calculating the limit of (x + log(x))/(x - 4), divided by x at x->+oo and x ->-oo
limx(x+log(x)x(x4))=0\lim_{x \to -\infty}\left(\frac{x + \log{\left(x \right)}}{x \left(x - 4\right)}\right) = 0
Let's take the limit
so,
inclined coincides with the horizontal asymptote on the right
limx(x+log(x)x(x4))=0\lim_{x \to \infty}\left(\frac{x + \log{\left(x \right)}}{x \left(x - 4\right)}\right) = 0
Let's take the limit
so,
inclined coincides with the horizontal asymptote on the left
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+log(x)x4=x+log(x)x4\frac{x + \log{\left(x \right)}}{x - 4} = \frac{- x + \log{\left(- x \right)}}{- x - 4}
- No
x+log(x)x4=x+log(x)x4\frac{x + \log{\left(x \right)}}{x - 4} = - \frac{- x + \log{\left(- x \right)}}{- x - 4}
- No
so, the function
not is
neither even, nor odd