/sci/ - Science & Math

Evening /sci/
During my multivariable calculus review session, someone (I suppose another tutor) wrote the following on the board and then explained a contradiction of it to my tutor (Can't into latex, so I'll try to word it as best as I can).

The union of A and B equals A implies that B is a subset of A.

Unfortunately I was barely paying attention to their conversation. So my question is, what is the contradiction? Or is this statement actually true?

Im stuck /sci/

here is where im at in this problem :
x^2+2x+1=(2 /sqrt x+4)^2

its two then the square root of x+4 squared
help someone??

I'm curious. How many practice problems do you all generally do in a given chapter/section before you believe you understand the material and move on?

Do you choose those that look the hardest, solve them, and then figure that the simpler problems aren't worth the wasted time? I ask because this seems to be the biggest time sink while learning any level of math.

What is your method/theory about practice problems?

I'm new to using LaTeX. Is there any easy way to show cancelled/crossed factors?

For instance:

[$]\frac{42}{24}[/$]
[$]\frac{2 \cdot 21}{2 \cdot 2 \cdot 2 \cdot 3}[/$]
[$]\frac{21}{12}[/$]

I want to cross out the first two factors in the second expression.

Thanks!

/sci/,
I've recently acquired an interest in Mathematics, but I am terrible in it (in the academic scenario).
I want to obtain more understanding in Math. Teachers in schools just tell us how to solve a problem, they don't tell us any kind of meaning. It's depressing, frustrating, and people get the notion of "What the fuck is this going to do for me?".
At any rate, I'm a junior in HS, and I feel as if I'm craving for some kind of understanding for Mathematics. Any help? Books? etc...

So /sci/, I am at a shit tier state university.
>inb4 retard
>inb4 you're fucked
It's a combination of being a stoner in high school and being a middle classfag. But I'm long over the stoner phase atm. I want to know what I should major in to increase my chances of getting into a decent-to-prestigious grad school/med school. I was thinking that I should double major in something very difficult to compensate for my shit-tier-uni status.

How well would these majors work out, if chose two and double majored in them:

* Mathematics
* Electrical Engineering (inb4 homosex)
* Chemistry
* Biology
* Mech-E