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/sci/ - Science & Math

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5566684 No.5566684 [Reply] [Original]

Okay, I'm trying to study for my discrete structures class, and this is just confusing to me. I get unions of sets for the most part, but this confuses me. An example he have was A = {x: x is a natural number and x =2j, and j is a natural number}. B = {x: x is a natural number and x = j^3 and j is a natural number}.
How am I supposed to go about finding A union B and A intersection B?

>> No.5566693

I tried just using Google, but everything that comes up is for simple problems where all of the elements are defined, not for these kinds of sets.

>> No.5566788

Test coming up soon. Any help would be appreciated.

>> No.5566792

A=even numbers
B=cube of numbers

intersection=numbers that are even and cubes, let's say even cubes (0, 8, 64, 216, ...)
union=numbers that are even or cubes (0, 1, 2, 4, 6, 8, 9, 10, ...)

>> No.5566797

>>5566684
Fuck your discreet structures class. I got a shitty professor who teaches at a turtle's pace. My class is full of morons, so he spent three weeks teaching binary addition, subtraction, and multiplication. The book we use is written by him and it's full of errors, so we have no resources for independent learning (he can't even recommend a good book). Enjoy that class.

>> No.5566845

>>5566792
I get that, but he wants an x = equation that works for it. He showed us once in class (same as he does for EVERYTHING) without showing us any real applications for it. He wants it to be A union B = {x: x is a natural number and x = something}. I have no idea how I'm supposed to figure it out. I hate this class.

>> No.5566857

>>5566797
Yeah I hate this class. He goes way too fast in this class. He gives us a general template and then moves on, after maybe one example. Then he goes on to the next one. Then, on homework or tests, he gives us real world applications that don't make sense to me. One example was "There are 50 tennis players. 34 are right handed and 42 serve underhand. How many are left handed and serve overhand?" It makes no sense. Wouldn't that be a probability and not have an exact answer?

>> No.5566875

how do you write that a number is an even cube with an equation involving, i dunno, another natural number j?

if x=j^3 and x is even, how about j?

>> No.5566936
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5566936

>> No.5566950

>>5566857
you sure he didn't also give the number of both right handed and underhanded too?

>> No.5566982

>>5566950
He didn't give us anything but what I typed there. So I don't know.

>>5566936
Ouch. I'm in CS because I want to be a game developer. I was originally a physics major but switched over.

>> No.5567187

>>5566936
Hahahaha

Don't you have some homework for your high school math class to attend to?

Engineering is for people too stupid to do real physics. CompSci has a lot more math than you think, and it has almost nothing to do with software development.

>> No.5567281

>>5566936
School is for people too stupid to be successful on their own.

>> No.5567302

>>5567281
I like this one

>> No.5567326

>>5567281
I am doing a lot of individual work on programming. I have bought books and have been working on my own indi game for some time now. However, a lot of workplaces require some form of degree. I honestly can't stand how college is set up, but I'm doing it anyway for that damn piece of paper.

>> No.5567404

I mean, really, giving you the answer here would end up hurting you. This information will be assumed in other courses if you're taking any more math. Look at the definitions once more until you understand them.