Graphing in Real Analysis

217 Views Asked by At

I am having trouble with the following question.

If we fix $a\in[-1,1]$ and define $h_a(x)=\frac{1}{2}(|x-a|+(x-a)))$

I am trying to sketch the graph of $h_{\frac{1}{2}}$ on $[-1,1]$

What does the $\frac{1}{2}$ refer to in $h_\frac{1}{2}$. Do I need to plug that in for $a$ in the equation $h_a(x)=\frac{1}{2}(|x-a|+(x-a)))$?

I have provided a link to a wolfram graph however I am not sure if this is correct or not,

https://www.wolframalpha.com/input/?i=1%2F2(%7Cx-a%7C%2B(x-a))+where+a%3D1%2F2

2

There are 2 best solutions below

9
On BEST ANSWER

Whenever a function has a modulus sign in it, you must consider separately the cases when the contents of the modulus is negative, and when it is positive. e.g. $y=|x|$ can be defined as $y=x , x\geq 0$ and $y=-x , x<0$

We have $f_{a}(x) = \frac{1}{2}[ |x-a|+(x-a)]$

Then $f_{\frac{1}{2}}(x) = \frac{1}{2}[ |x-\frac{1}{2}|+(x-\frac{1}{2})]$

We have two cases to consider:

Case $(1)$: $$x-\frac{1}{2} \geq 0 \implies x\geq \frac{1}{2}$$

Case $(2)$: $$x<\frac{1}{2}$$

Note that in general:

$|x| = x$ for $x \geq 0$ and $|x| = -x$ for $x<0$

So firstly consider case $(1)$:

$|x-\frac{1}{2}| = x-\frac{1}{2} \implies f_{\frac{1}{2}}(x) = \frac{1}{2}[ x-\frac{1}{2}+x-\frac{1}{2}] =x-\frac{1}{2}$

Then consider case $(2)$:

$|x-\frac{1}{2}| = \frac{1}{2} - x \implies f_{\frac{1}{2}}(x) = \frac{1}{2}[ -x+\frac{1}{2}+x-\frac{1}{2}] = 0$

So for $x\geq \frac{1}{2}, f_{\frac{1}{2}}(x) = x-\frac{1}{2}$

and for $x<\frac{1}{2}, f_{\frac{1}{2}}(x)=0$ which should be simple to sketch

4
On

Yes, the $1/2$ in the equation means that you plug it in for $a$ in the equation. The wolfram graph looks correct.