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[Simetrical]

I had only been introduced (horribly) to Algebra a year ago, so no fancy crap please.


In a problem like:

2(7x-4) = (irrelevant)

When you simplify the first party, does the 4 become negative or does it remain positive?

If by "simplify" you mean "distribute", the −4 becomes −8, as Tiberius says. You have to multiply every term of the thing in parentheses by 2, i.e.

2·(7x − 4) = 2·7x − 2·4 = 14x − 8.

This goes for any number of terms, and you have to keep any minus signs you have:

−7·(2x³ + 5x² − x + 4) = (−7)·2x³ + (−7)·5x² − (−7)·x + (−7)·4
= −14x³ − 35x² + 7x − 28.

Why would you want to do that? Much easier to just divide the whole thing by two...

It depends on what you're doing. If the full equation were

2(7x − 4) = x² + 7

then you'd want to distribute and bring everything to one side so you could apply the quadratic formula. If it were

2(7x − 4) = 0

then clearly you'd want to divide by 2 first thing.

[Wheelchair]

Hey I'm doing a consumerism project about taxes and the likes, heres a quick question I need help with.

If you invest $6000 at 7.5% compound weekly, what would your investment be worth in 10 years?

[Orgath]

6000(1+(.075/52)^(520)

compound interest formula

[Simetrical]

To nitpick, in a ten-year period there will be either 521 or (more likely) 522 weeks, not 520. A year is 52 weeks and one day, or two days for a leap year, so you end up with 12 or 13 extra days (depending on whether there are two or three leap years in the ten-year period) in addition to 520 weeks.

[Orgath]

I don't think Wheelchair is doing that complicated of a math problem. I'm assuming this problem is straight from an Algebra II textbook. I suppose he could always check the back of the book!

[So Much Fire]

A little bit tougher this time.... a friend asked me for help with her biology homework, it's for her finals week and she got a section of a paper she needs to fill in a chart with properties of Bacteria, Fungi, Protozoa and Virii. Needed are "conditions for growth", "movement", and "resistance in unfavourable conditions" for virii. I'm guessing conditions for growth for virii in general would be similar to HIV, movement I couldn't even begin to answer, and the resistance I'm not sure either, but it might have to do with if a virus is considered living or non-living. Thanks in advance!

[Bernem]

so, viri won't grow, they replicate in in eu- or procaryotic cells, the can't move on their own.
you'll have to specify what you mean with resistance though. Is it rather resistance against environmental conditions, or is it resistance against toxins which would specificly work against pro and eucaryots, but not viri?

[So Much Fire]

Resistance in unfavourable conditions as in how they survive basically. For example when someone comes down with a virus, why certain ones take a while to be fought off completely. I actually had one a while ago, and all the doctors said to do was treat the symptoms and not the cause since for some reason they couldn't prescribe meds to deal with the infection itself, while it took 2 weeks to fight off completely. How it managed to survive once in my body to provide a clearer example.

[Bernem]

viri don't have a metabolism, against which many antibiotics work, and they are using your replication system, which you wouldn't want to block. Many viri hide inside your cells and are therefore not susceptible to medicine (or even your immune system), so in many cases the only thing a doctor can do is to treat some extreme symptoms (like high fever).

To summarize a virus infection (roughly):

1. the virus enters your body through body opening or wounds
2. the virus adheres to your body cells and enters them (many possible ways)
3. the viral genome is read and replicated by your cells. Many viral protein products can impair your cells' reactions against a viral attack.
4. new virions (1 unit of infectious virus) are assembled in your infected cells
5. the cells release the assembled virions (and usually die in this process). this together with your immune reaction increases the effect of the infection
6. the virions attack the neighbouring cells --> after some time your immune system can manage to destroy the virions and the infected cells. You are cured and in many cases you aquire an immunity against this type of virus.
7. some viri (such as herpes) can 'hide' inside your cells without replicating. That means that they don't kill these cells and they don't allert your immune system and only break out angain when your immune system is weakened.
8. HIV preferably infects T-Cells (an important sort of immune cells) and weakens your body over time by eradicating the T-Cells, which are crucial in promoting persistant immunity and immune responses.


Hope that helped!

[Eupholi]

Any help with my Bio class would be much appreciated, the answer does not need to be long. This are post-dissection questions of the brain.

1) Explain the significance of difference in colour of the two regions of the cerebellum and it's relationship to the convultions.

2)Explain why the corpus callosum is only one colour.

[Bernem]

well neuro is not exactly my favorite (anymore), but a short read brings it back....

1) the cerebellum has a cortex (grey matter) that consists of the neuronal cell bodies and a medulla (white matter) that consists of Axons, as the cell bodies lie on the outside of the cerebellum the convolution increases the area where cell bodies can be located and therefore their number.

2) the corpus callosum is the connection between the two brain hemispheres. this connection is obtained by Axons therefore the color of C. c. is white --> there are no cell bodies

it's relatively well described on wikipedia:

http://en.wikipedia.org/wiki/Cerebellum

http://en.wikipedia.org/wiki/Corpus_callosum

[Eupholi]

Looked in wikipedia but didn't quite understand it.

Thanks for help

+rep

[Bernem]

You're welcome, I hope you understood it from my description. If not feel free to ask!

[So Much Fire]

Thanks Bernem

[Bernem]

You're welcome!

[julmoo]

Help!

So I just found out that my teacher plans a chemistry test for tomorrow, well there is a little problem.

He will ask about the pH-value....but he didn't explain anything at all and I have no idea how to find it out
I already looked on the internet for something but I didn't get all that stuff, it's too complicated

Can anyone explain me how to figure out the pH-value of something?

the only thing I know is:
K= ([H3O+]*[OH-])/[H2O]²=
([10^-7]*[10^-7])/[55,5]²

Thankies!

[julmoo]

Umm.....can also someone explain what Iones are and how I can find out how many there are (for example Al, Si, Cu, CO2)

And that is "Titration"??

[Phileas Fogg]

I need help in Optics [physics].

A biconcave/plano-concave lens, 2.5+ dioptre, is infront of an object which is 8 centimeters tall, reflects the object's Optical Image in the size of 4 centimeters.

A. What is the distance of the object from the lens?
B. What is the ditance of the Optical Image from the lens?
C. What is the character of the Optical Image [Virtual/Real; Enlarged/Reduced; Normal/Reversed]?

Thanks in advance!

Umm.....can also someone explain what Iones are and how I can find out how many there are (for example Al, Si, Cu, CO2)

Every element can be Ion. An Ion is an element, or a molecule [for instance, NO3−) which has lost or gained one [or more] electrons then usually existed - which means they equat in numbers to the number of Protons*. Since electrons have negative electric charge, an element (or a molecule) with an additional electron will have minus above it [as NO3−), while an element or a molecule having less electrons then normal will have a plus above it.

*The numbers of the elements in the periodic table is acorrding to the number of Protons. For instance, Iron [F in the periodic table] is number 26 in atomic numbers, which means it consists 26 Protons and 26 electrons.

Hope its clear now.

[ajm317]

I need help in Optics [physics].

A biconcave/plano-concave lens, 2.5+ dioptre, is infront of an object which is 8 centimeters tall, reflects the object's Optical Image in the size of 4 centimeters.

A. What is the distance of the object from the lens?
B. What is the ditance of the Optical Image from the lens?
C. What is the character of the Optical Image [Virtual/Real; Enlarged/Reduced; Normal/Reversed]?

Thanks in advance!

Two equations you may find useful are:

M=-S₂/S₁
1/S₁+1/S₂=1/f (the thin lens equation)

Where M is the magnification, and is positive when the image is upright and negative when it is inverted, S₁ is the (positive) distance between the object and the lens, S₂ is the distance from the lens to the image and is positive when the image is located on the opposite side of the lens from the object and f is the focal length of the lens, where 1/f is the dioptre.

[julmoo]

electrons then usually existed - which means they equat in numbers to the number of Protons*. Since electrons have negative electric charge, an element (or a molecule) with an additional electron will have minus above it [as NO3−), while an element or a molecule having less electrons then normal will have a plus above it.

*The numbers of the elements in the periodic table is acorrding to the number of Protons. For instance, Iron [F in the periodic table] is number 26 in atomic numbers, which means it consists 26 Protons and 26 electrons.

Hope its clear now.

Okay! Thanks ^^

I think I got it now