Bryn

what's the proof for the discriminant [math]b^2-4ac[/math]? e.g. Proove that if [math]b^2 > 4ac[/math] then x has 2 real and distinct roots.

so n=8?

In 1980 a river was restocked with fish. The local angling club kept a record of the number of fish, y caught on a stretch of the river t years after restocking. Some of the records are given in the table below. t 1 2 3 4 5 7 10 12 y 185 170 172 166 164 159 162 157 The regression line y on x is y=177.28 -1.89t An alternative model is produced using the new variable x=1/t which gives the following SUM(x) = 2.6095 SUM(x^2) = 1.5010 SUM(y) = 1335 SUM(xy) = 453.6310 Caluculate the regression equation of y on x in the form y = a+bx ----- I got the equation y = 73+175x when using n=12 (as the max of t is 12) but the answer is y = 158 + 28x. What value of n do i use for caluclulating Sxx and Sxy?

I'd eat the vinegar and baking soda and let my muscles do the rest. (vinegar is nice byitself, tho i've never tried baking soda by itself )

In an ionic solid all the atoms are bonded to all the atoms around it. This is true thorught the entire solid, so in effect everything is bonded together. If you used to number of actual atoms in the chemical formula you'd be using rather large numbers in the billions, which would make the formula rather long winded. Using ratios just makes things so much simplier. If you need to know how big the solid is you can say it has blah blah number of moles in it, which is a far easier way of doing things. as for the second question, the term molecule is used rather loosly for ionic compounds. When describing the type of solid you can have giant ionic, giant molecule, as well as ionic and molecule, which means different things. But you can use the term "a molecule of sodium chloride" sodium chloride being an ionic solid. So i'd use the term molecule in relation to ionic compounds loosly, it can sorta apply but it can also sorta not apply, if you see what i mean (which may be difficult )

what type of RNA is iRNA when it's at home? Yes it is quite possible to use viruses as vectors. Generally the virus would need to be included in the DNA, and have a promoter associated with it. There is evidance of thousands of viruses in our DNA already that have hitched a ride on us. Most are not expressed but it would be quite possible for a promoter to be assocaited with the virus to express it. There's plenty of research into this ongoing, not sure if anyone has suceeded yet. afaik all the viruses being used loose there infectioness when they are altered to included the DNA that needs to be inserted. But i'm sure it's quite possible, tho very hard. You probably wouldn't get much of a choice about which genes you wanted to surpress, it'd be more luck in getting a viruses that surpresses a gene and is still infectios. By the time we have the skill to produce viruses from scratch that do the job we want the whole point may be rather mute, as with that kinda skill we would be able to alter our DNA willy nilly any way.

yea but 1.96 is sigma squared isn't it? so to get sigma you need the sqrt. is it not in the format X ~ N(u , sigma^squared) ?

If X has the distribution N(102.3,1.96), calculate P(X<100) Now to get the standard normal distribution it's (100 - mew)/sigma so should be (100-102.3)/SQRt(1.96) ... P(Z<-1.64) That is correct isn't it? It's just that the book as got an answer that indicates they've used 1.96 instead of SQRT(1.96), but 1.96 is sigma squared right? btw is there anyway to do all the mathematical symbol, list sqare root, sigma, mew etc.

ah ok cheers

i used y-y1 = x-x1 y2-y1 x2-x1 to get y = 3+12x/pi How did you get -3 and 3?

y = psinx + qcosx passes through the points (0,3) and (pi/4,0). Find the values of p and q. Using formula on the coordinates i've got y = 3 + 12x/pi so psinx + qcosx = 3 + 12x/pi but then where? only 2 identities i need for this course is sinx/cosx = tanx and (sinx)^2 + (cosx)^2 = 1 but i cant see how i can use these

Sounds fasinating. But i didn't understand most of it :o/. What subject are you studying to do that kinda stuff?

Well presumably the egg can't be fertilized until it is fully grown, as in human egg cells. So the egg is grown, then you don't let the chicken bonk anyone, and so the egg can't be fertilised. It could also be because humans have bred them that way over thousands of years, those that don't lay unfertilised eggs either get eaten for sunday lunch or don't get the protection of humans and so have a disadvantage.

Ah, so how big is the egg cell in a chicken egg?

Not too sure but i think it's because if you strip hydrogen of it's electron it becomes just a proton, with a high densitiy of positive charge. That positive charge then just pulls those electrons straight back again until there in a region inbetween the two nuclei.

For a rather large number of cell divisions the feotus does not grow in size, it just splits the existing cytoplasm in two. The same undoubtedly happens for the chickens. So the egg can be an egg cell, and it divides and differentiates into tissues but doesn't grow. Infact it can't grow as it has no external food source, only what's already in the egg, that why there is so much food and protein in an egg.

Time reversibility

Well the bulb in a flashlight is enclosed anyway so evan on earth convection won't cool it down. If you have electronics in the vacum surley the fact that it's only 3 degrees above absolute zero helps cool it down a bit? Unless you have a heated vacuum, which seems a little silly, and tbh how the fuck would you heat a vacuum in the first place?

Cos the air is colder than the water so it'll freeze on top, then as ice is lighter than water it'll float.

nevermind, got it now.

A man draws one card at random from a complete pack of 52 cards, replaces it and then draws another card at random from the pack. Calculate the probibility that eaxactly one of the cards is a Queen. I evaluated P(Q n Q') = 1/13 * 12/13 (they are independant events) =12/169 The answer according to the book is 24/169 . Help!

try centrifuging an egg to get some mitochondria from it.

and some protocista have chlorophyll

Glucose is by no means the sole product of photosynthesis. The main product is Triose Phosphate which can be used to make carbohydrates (e.g. glucose), amino acids and lipids. The light dependant stage takes place in the thykloid membrane, which is those flat pankcake like things inside the chloroplast. The light independant stage (which is a far better name than the misleading dark reaction) occurs in the watery matrix of the chloroplast called the stroma. I'm guessing the oxygen leaves by the same route the CO2 entered, by plain old diffusion out through the holey things in the underside of the leaf that I can't remeber the name of right now...

If there are other aliens close by it's quite possible they would be alot like us. Dunno if it's been proven but it's certainly a theory that simple bacteria/viruses or just bits of RNA/DNA could be flung out from whether they evolved into space and then populate other worlds. So they would have a similiar basically molecular/cellular structure to us. So there could easily be aliens like us, not perhaps strictly humanoid in structure but closer than you might think. If the above is possible i think it'd be a lot more probably that aliens living locally would be related to us than aliens who have evolved of there own accord.