Mister Exam
Graphing y = xln(x-x^2)
The solution
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/ 2\ f(x) = x*log\x - x /
$$f{\left(x \right)} = x \log{\left(- x^{2} + x \right)}$$
f = x*log(-x^2 + x)
The graph of the function
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:
$$x \log{\left(- x^{2} + x \right)} = 0$$
Solve this equation
Solution is not found,
it's possible that the graph doesn't intersect the axis X
so we need to solve the equation:
$$x \log{\left(- x^{2} + x \right)} = 0$$
Solve this equation
Solution is not found,
it's possible that the graph doesn't intersect the axis X
Extrema of the function
In order to find the extrema, we need to solve the equation
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(the derivative equals zero),
and the roots of this equation are the extrema of this function:
$$\frac{d}{d x} f{\left(x \right)} = $$
the first derivative
$$\frac{x \left(1 - 2 x\right)}{- x^{2} + x} + \log{\left(- x^{2} + x \right)} = 0$$
Solve this equation
Solutions are not found,
function may have no extrema
$$\frac{d}{d x} f{\left(x \right)} = 0$$
(the derivative equals zero),
and the roots of this equation are the extrema of this function:
$$\frac{d}{d x} f{\left(x \right)} = $$
the first derivative
$$\frac{x \left(1 - 2 x\right)}{- x^{2} + x} + \log{\left(- x^{2} + x \right)} = 0$$
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
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative
$$\frac{2 + \frac{2 \left(2 x - 1\right)}{x} - \frac{\left(2 x - 1\right)^{2}}{x \left(x - 1\right)}}{x - 1} = 0$$
Solve this equation
The roots of this equation
$$x_{1} = 1 - \frac{\sqrt{2}}{2}$$
$$x_{2} = \frac{\sqrt{2}}{2} + 1$$
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
$$\left(-\infty, 1 - \frac{\sqrt{2}}{2}\right]$$
Convex at the intervals
$$\left[1 - \frac{\sqrt{2}}{2}, \infty\right)$$
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative
$$\frac{2 + \frac{2 \left(2 x - 1\right)}{x} - \frac{\left(2 x - 1\right)^{2}}{x \left(x - 1\right)}}{x - 1} = 0$$
Solve this equation
The roots of this equation
$$x_{1} = 1 - \frac{\sqrt{2}}{2}$$
$$x_{2} = \frac{\sqrt{2}}{2} + 1$$
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
$$\left(-\infty, 1 - \frac{\sqrt{2}}{2}\right]$$
Convex at the intervals
$$\left[1 - \frac{\sqrt{2}}{2}, \infty\right)$$
Horizontal asymptotes
Let’s find horizontal asymptotes with help of the limits of this function at x->+oo and x->-oo
$$\lim_{x \to -\infty}\left(x \log{\left(- x^{2} + x \right)}\right) = -\infty$$
Let's take the limit
so,
horizontal asymptote on the left doesn’t exist
$$\lim_{x \to \infty}\left(x \log{\left(- x^{2} + x \right)}\right) = \infty$$
Let's take the limit
so,
horizontal asymptote on the right doesn’t exist
$$\lim_{x \to -\infty}\left(x \log{\left(- x^{2} + x \right)}\right) = -\infty$$
Let's take the limit
so,
horizontal asymptote on the left doesn’t exist
$$\lim_{x \to \infty}\left(x \log{\left(- x^{2} + x \right)}\right) = \infty$$
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*log(x - x^2), divided by x at x->+oo and x ->-oo
$$\lim_{x \to -\infty} \log{\left(- x^{2} + x \right)} = \infty$$
Let's take the limit
so,
inclined asymptote on the left doesn’t exist
$$\lim_{x \to \infty} \log{\left(- x^{2} + x \right)} = \infty$$
Let's take the limit
so,
inclined asymptote on the right doesn’t exist
$$\lim_{x \to -\infty} \log{\left(- x^{2} + x \right)} = \infty$$
Let's take the limit
so,
inclined asymptote on the left doesn’t exist
$$\lim_{x \to \infty} \log{\left(- x^{2} + x \right)} = \infty$$
Let's take the limit
so,
inclined asymptote on the right doesn’t exist
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:
$$x \log{\left(- x^{2} + x \right)} = - x \log{\left(- x^{2} - x \right)}$$
- No
$$x \log{\left(- x^{2} + x \right)} = x \log{\left(- x^{2} - x \right)}$$
- No
so, the function
not is
neither even, nor odd
So, check:
$$x \log{\left(- x^{2} + x \right)} = - x \log{\left(- x^{2} - x \right)}$$
- No
$$x \log{\left(- x^{2} + x \right)} = x \log{\left(- x^{2} - x \right)}$$
- No
so, the function
not is
neither even, nor odd