 Lv 31,128 points

# ?

• ### Can you explain the American Maths teaching system?

I've seen questions with things like "help with Algebra I" and people answering them saying "I only understood this after Algebra II".

How does this system work? Do you get to choose which areas of maths you study? How old are you when you do these courses? What are the other options?

• ### 6 lamps in parallel circuit - help with power please!?

I have 6 lamps (bulbs) arranged in parallel, with a switch on each branch (to accompany each bulb). They are all rated 20W.

I think my question might be stupid, but do the bulbs always take 20W? i.e: If I apply 20V they will draw 1A, if I apply 200V they will draw 0.1A? Is this right?

Cheers.

• ### Set theory - disputing wikipedia. Help please!?

at http://en.wikipedia.org/wiki/Table_of_mathematical... (just below half way down the page) The explanation of the set of real or complex numbers (K) is given as:

"(x^2) belongs to the set of complex numbers (C) for all x belonging to K because (x^2) belongs to C for all x belonging to R and C"

My apologies for not using the actual symbols.

I do not understand this becasue it implies any number x, whether complex or real, when squared, will be complex. This is obviously not true because any real number squared gives another real number.

Am I missing something? If so, could you explain it to me please?

PS: I know all real numbers belong to the set of complex numbers (ie R is a subset of C) by letting the complex part be zero, but if this is what I'm missing, what is the point in the set K?