## http code 400 – Why do I get 400 errors on root requests?

In my log, I sometimes see a 400 error generated for what appears to be a valid request. For example:

``````"GET / HTTP/1.1" 400
``````

This is a valid request on my site which normally returns the home page. Why would I see error 400. Is it due to bad syntax in the request header?

## is it possible to delete a file from the system folder without being root?

I found this file: /system/recovery-from-boot.p and I read that this prevented me from entering recovery mode, but since I am not root , I can't find a way to delete it or rename it … a suggestion, please?

## meta tags – Good SEO practices for a root page that detects the language and redirects

I have a multilingual static website; the pages of each language live in specific sub-folders such as / en, / es, / fr, etc.

In my idnex root page, I dynamically detect the user's language (via Javascript) then I redirect to the appropriate language specific folder.

What should I think about in terms of SEO for this index page?

• Should I add hreflang attributes pointing to the index page in the language-specific subfolders?
• What should I add as x-default? One of the language-specific index pages, or the "language detection" page itself (which has no actual content ..)
• Should I add a robots meta tag?

## Common points of the algebraic set defined by the common root of a family of polynomials

I am struggling with a combination of definitions in a document.

In the preliminaries, the author defined:
"we write Zer (P) for the algebraic set defined by the common roots in R of a family P of polynomials with coefficients in R"

Later he says that we have to "determine the commonalities of Zer (H2) and
Zer (H3) as well as the topology of Zer ( tilde (Sil (Q1)) and Zer ( tilde (G)) "(page 12 first and second line). Sil (Q1) and G are polynomials and H2 and H3 are the sections of two polynomials.

I don't understand what the Zer (-) sets have in common and how to calculate the topology using the TOP algorithm.
Recently, I assume that the set Zer (-) are disjoint points and not a polynomial. It may be wrong and I would be very happy if someone could present a very basic example.

Thank you so much.

## root access – Unable to activate developer mode on Nexus 7 2013 by pressing the build number

I'm trying to root the Nexus 7 2013 and for the purpuse which I need to enable USB debugging. According to instructions from several resources, activate developer mode it is necessary press the build number 7 times. Has done this a lot of times, but nothing happens.

I saw this other question on this, where the case seemed to be that there were multiple users, but in my case there is only one user on the tablet .

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## fit – Implement a function that imports data from the same web page root

I would like to implement a function to import multiple datasets from the same website source, where for each dataset it only changes one word on the website address.

Here is the website: `https://statistichecoronavirus.it/regioni-coronavirus-italia/.../`
or `...` represents the part to be modified to obtain each data set.
I would like to have the following variable vectors from each web page:

``````total infected
total active cases
total deaths
total healed
daily increment infected
daily incremental active cases
daily increment deaths
daily increment healed
``````

I tried to write the following, but it doesn't work:

``````covid19(region_) :=
Module({data, process, date, infected, cases, deaths, healed},
data = Import(
"https://statistichecoronavirus.it/regioni-coronavirus-italia/"<>region <> "https://mathematica.stackexchange.com/", "Data");
process(s_String) := Module({d = StringSplit(s, " ")((1))},
If(StringContainsQ(d, "https://mathematica.stackexchange.com/"),
DateObject({d <> "/2020", {"Day", "https://mathematica.stackexchange.com/", "Month", "https://mathematica.stackexchange.com/", "Year"}}),
ToExpression(StringReplace(d, "." -> ""))));
process(s_Integer) := s (*to process the last string*);
date = Map(process, data((2, All, ;; -2)), {2})((All, 1));
infected= Map(process, data((2, All, ;; -2)), {2})((All, 2));
cases = Map(process, data((2, All, ;; -2)), {2})((All, 3));
deaths = Map(process, data((2, All, ;; -2)), {2})((All, 4));
healed = Map(process, data((2, All, ;; -2)), {2})((All, 5));
<|region -> <|"Infected" -> infected, "Cases" -> cases, "Deaths" ->deaths, "Healed" -> healed|>|>)
status = covid19 /@ {"Lombardia", "Sicilia"} // Association;
``````

This is what I did without functional programming bases:

``````ClearAll;
data = Import("https://statistichecoronavirus.it/coronavirus-italia/",
"Data");
Table(Drop(%((2, i)), -1), {i, 1, Length(%((2))) - 1});
temp = Table(StringReplace(%((i)), "." -> ""), {i, 1, Length(%)});
StringExtract(##, 1) & /@ temp;
Join({data((1, 2 ;; All))},
ToExpression(%((All, 2 ;; All))), {ToExpression(
Drop(data((2, -1)), -1)((2 ;; All)))});
tot = Transpose(
Insert(% // Transpose,
Flatten({"Data", StringExtract(##, 1) & /@ temp((All, 1)),
"20/02"}), 1));
contagi = tot((2 ;; All, 2));
casi = tot((2 ;; All, 3));
morti = tot((2 ;; All, 4));
guariti = tot((2 ;; All, 5));
Join({data((1, 2 ;; All))},
ToExpression(
ArrayReshape(
StringCases(StringJoin(temp),
Shortest("(+" ~~ x__ ~~ ")") -> x), {Length(temp),
4})), {ToExpression(Drop(data((2, -1)), -1)((2 ;; All)))});
par = Transpose(
Insert(% // Transpose,
Flatten({"Data", StringExtract(##, 1) & /@ temp((All, 1)),
"20/02"}), 1));
(CapitalDelta)contagi = tot((2 ;; All, 2));
(CapitalDelta)casi = tot((2 ;; All, 3));
(CapitalDelta)morti = tot((2 ;; All, 4));
(CapitalDelta)guariti = tot((2 ;; All, 5));
date = Table(
DateObject({tot((i, 1)) <> "/2020", {"Day", "Month", "Year"}}), {i,
2, Length(tot)})
G1 = TemporalData(contagi, {date});
G2 = TemporalData(casi, {date});
G3 = TemporalData(morti, {date});
G4 = TemporalData(guariti, {date});
Show(ListLinePlot(G1), ListLinePlot(G2), ListLinePlot(G3),
ListLinePlot(G4))
Interpolation(G1, InterpolationOrder -> 4)
``````

My final goal is to get multiple interpolation and best fit functions for each region.
I would avoid repeating it for each "region".

## Context

I frequently install new roms and often have to wipe my phone. So I was looking for a good backup solution to back up all the apks of my app, because I don't have enough bandwidth to re-download all the apps. I don't care about losing locally stored data, since most of my apps only need a connection to sync. `adb backup` leaves many apps, so I decided to write a script that manually extracts the apks from the device.

Something like –

``````adb shell cmd package list packages
adb shell cmd package path \$package
adb pull \$package // I have a loop here to pull every APK in the path
``````

## The problem

habitually `adb pull \$package` works, as long as the apk is in `/data/app/\$package-dir`. The problem is that I have an external SD card as adopted storage. The SD card is at `/mnt/expand/\$UUID`and the apks of certain applications are stored in `/mnt/expand/\$UUID/app/\$package-dir/`. Trying to fire these apks will result

adb: error: unable to rule the remote object & # 39; /mnt/expand/\$UUID/app/\$package-dir/base.apk&#39 ;: authorization refused

How can i shoot from `/mnt/expand/\$UUID/app/\$package-dir` rootless?

## algorithms – Why do we find the square root of the perfect square \$ O (M (n)) \$

I have seen this question and its answer on the stack swap of theoretical computing and I do not understand why the complexity of finding the root is the same as that of a multiplication. I thought we might need more $$O (1)$$ multiplications to find the root (using Newton's iteration as shown in the answer, as the method may require more than $$O (1)$$ not).

Is there an upper limit not dependent on $$n$$ how much multiplication we might need? Or a method to find the root with sufficient precision (which means finding the real root) after $$O (1)$$ not? Am I missing something?

Note: I did not ask this question about the theoretical CS stack exchange, as it is meant to be intended for professional CS researchers and no one asked in the comments, so suppose that it is not a question of level of research even if it is an explanation of a (question at the level of research).

## root access – i just pulled my phone out of a bootloop, should i flash magisk or is it too risky?

My phone was stuck on a bootloop, and I fixed it by typing adb reboot bootloader in cmd.
I didn't even type that, Bi typed adb reboot bootloade and forgot the r but it still worked.
I'm just wondering because I won't have another phone if it's masonry or stuck in a bootloop, is it too risky to flash magisk or?