# ABCD1234pop

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1. ## Matrix question. ACA-AB=0. What's C?

I know how to find A inverse. And I know ACA=AB. But how do I go through solving this? I figured it had something to do with the inverse of A. But matrix multiplication isn't the same as normal multiplication. Will something like (Inverse of A)ACA=(Inverse of A)B Since (Inverse of A)A=The identity Matrix CA=B Then CA(Inverse of A)=B(Inverse of A) C=B(Inverse of A) I'm pretty sure all of this is wrong, but even if it isn't, I'm stuck here. How can I solve this and similar questions?

Oh, never mind. I forgot you had to transpose it at the end.

This is what I did... Should it be -5? What am I doing wrong?
4. ## Why do different elements have different properties?

Yes, but WHY does it behave differently?
5. ## Why do different elements have different properties?

I know that it's because of their different atomic structure, but why? I think I have an idea of why specific properties are present in some elements, like radioactivity(because of their instability) or reactivity with other elements(because of their electron configuration) or atomic weight (because of the number of protons and neutrons)...etc. But how do any of those(or something else I'm most likely unaware of) explain color, texture, melting points and boiling points, density, and many other properties I can't think of at the moment(what are the other properties?). Like, why is gold's color different than silver? I don't know much about science, besides a few things I read here and there. What field of science would answer these questions? I figured it would be chemistry, but would physics give a more basic answer, as it underlines chemistry? Also, how many years would it take me to have a firm understanding of physics? I'm thinking of starting out soon. How would you suggest I begin? I didn't think I was smart enough so I haven't bothered up until now. How hard is it going to be? Thanks anyway.
6. ## Summation

I tried solving it. But I also did it with a calculator and it tells me the result is 81. What am I doing wrong? EDIT: I didn't know you could do that. I don't know anything about the laws of summation. I figured out what I did wrong. Here's my edited answer. I confirmed it with a calculator and it's correct. Yay!
7. ## Summation

How do I solve this one? EDIT: I tried this, I don't think it's right.
8. ## Why is the speed of light...

300,000Km/s ? Why isn't it some other number?
9. ## The Universe expanding and time...

Assuming spacetime expands at different speeds at different directions, would Person X (The guy where spacetime is expanding faster)age slower than person Y(The guy where spacetime is expanding slower)? Thanks again.
10. ## The Universe expanding and time...

Would things stop moving if the universe stopped expanding? And does the universe accelerate at the same rate in its expansion everywhere? Thank you.
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