# Logic

#### JeffM

##### Elite Member
I don't understand what you mean.

Please post the complete exercise statement. There is no exercise statement. He is trying to find ways to contradict basic axioms.

#### pka

##### Elite Member
There is no exercise statement. He is trying to find ways to contradict basic axioms.
I am very reluctant to call names. But Ryan$takes the cake S/he is by any means of the imagination an InterNet TROLL. Please, please follow that LINK. If anyone can argue that Ryan$ fails to fulfill that definition of a TROLL please post your justifications.
Ryan$has the mind of a child. … from equation logic … x=2y … … logic [lets me] do whatever … … I can think in general … so it's possible [that x≠2y] #### JeffM ##### Elite Member Ryan$ has the mind of a child. I suspect that he is a child. I have not seen malicious intent.

#### mmm4444bot

##### Super Moderator
Staff member
I suspect that he is a child. I have not seen malicious intent.
Agree!

We've asked Ryan$to follow the guidelines, so tutors can know what he's talking about. I intend to start enforcing those requests. • topsquark #### Subhotosh Khan ##### Super Moderator Staff member Agree! We've asked Ryan$ to follow the guidelines, so tutors can know what he's talking about. I intend to start enforcing those requests. Not a basic face - neither an acidic face - just a neutral face (pH = 7) - as clear as water

• mmm4444bot

##### Full Member
Hi guys, before you think that I troll, it's really serious and not trolling at all.
lets assume I have three equations like this:
(1) x=5
(2)x=3*m +6
(3) x+y=7
I conclude from first equation that x=5, ye? i'm find with this!
now I go to third equation, x+y=7 ! who said that I can refer to the first equation x=5 and assign it on that equation?
we already discuss "if we don't know anything about something, then we assume generally it's true" , so if it's true to not refer first equation x=5, and assign it on third equation x+y=7 , then why we are using/referring what we have from equation (1) to equation 3 while it's true to not refer?! (why it's true to not refer? because none tells me that I can refer equation (1) to equation (3), so generally what every possibility I take would be true .. so if I don't want to refer to first equation to solve equation (3), then it's true ... so why we aren't taking that possibility(to not refer to first equation in order to solve equation (3) )?!

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#### lev888

##### Senior Member
The problem statement should instruct you to solve either
1. A set of equations or
2. A system of equations (simultaneous equations)
Only in the case of a system of equations can you use one equation to solve another - they have a common solution by definition.

#### JeffM

##### Elite Member
Hi guys, before you think that I troll, it's really serious and not trolling at all.
lets assume I have three equations like this:
(1) x=5
(2)x=3*m +6
(3) x+y=7
I conclude from first equation that x=5, ye? i'm find with this!
now I go to third equation, x+y=7 ! who said that I can refer to the first equation x=5 and assign it on that equation?
It's a problem that YOU made up so you tell us whether or not you can refer to a previous equation.

we already discuss "if we don't know anything about something, then we assume generally it's true"
What in the world are you talking about? Who said that? It is WRONG.

, so if it's true to not refer first equation x=5, and assign it on third equation x+y=7 , then why we are using/referring what we have from equation (1) to equation 3 while it's true to not refer?! (why it's true to not refer? because none tells me that I can refer equation (1) to equation (3), so generally what every possibility I take would be true .. so if I don't want to refer to first equation to solve equation (3), then it's true ... so why we aren't taking that possibility(to not refer to first equation in order to solve equation (3) )?!
This is why people think you are trolling: none of that makes any sense at all.

I have a guess. You do not fully understand that in different problems x may, and usually does, refer to different numbers.
Variables are NOT numerals. 3 always refers to the same specific number. On the other hand, x refers to the same specific number only for the duration of a single problem.

I strongly suggest that you give us problems that come from your teacher or text and confuse you and then try to tell us what confuses you about those problems. The problems that you make up on your own make no sense and so do not allow us to see where exactly your confusion lies.

• topsquark

#### HallsofIvy

##### Elite Member
Hi guys, before you think that I troll, it's really serious and not trolling at all.
lets assume I have three equations like this:
(1) x=5
(2)x=3*m +6
(3) x+y=7
I conclude from first equation that x=5, ye? i'm find with this!
now I go to third equation, x+y=7 ! who said that I can refer to the first equation x=5 and assign it on that equation?
Un- no one did! Where did you get that idea? Unless, of course, we are told that these are "simultaneous equations"- that is that the equations are true for the same values of x, y, and m.

we already discuss "if we don't know anything about something, then we assume generally it's true"
WHO discussed that? Because that's a really foolish thing to assume! "If we don't know anything about something" then we can't assume anything about it. UNLESS, again, we were told that these are simultaneous equations and are told that they are true for the same values of x, y, and m
.
, so if it's true to not refer first equation x=5, and assign it on third equation x+y=7 , then why we are using/referring what we have from equation (1) to equation 3 while it's true to not refer?! (why it's true to not refer? because none tells me that I can refer equation (1) to equation (3), so generally what every possibility I take would be true .. so if I don't want to refer to first equation to solve equation (3), then it's true ... so why we aren't taking that possibility(to not refer to first equation in order to solve equation (3) )?!
I don't understand what you are asking because you haven't said what problem you are trying to solve! You give three equations in x, y, and m. Are they "simultaneous equations"? If they are then they must all three be true for the
same values of x, y, and m. Since x= 5, x+ y= 5+ y= 7 so y= 2. Then x= 5= 3m+ 6 so 3m= 5- 6= -1 and m= -1/3. If we are told that these are "simultaneous equations" then x must be 5, y must be 2, and m must be -1/3. But we have to be told what problem we are solving!

• topsquark

##### Full Member
what do you mean by senseable?! not make sense? you mean "not logically" ?!

#### JeffM

##### Elite Member
I do not want to get into the relationship between logic and mathematics. It is complicated. All I shall say is that logical implication is not what an equal sign means.

"If Toto is a dog, then Toto is an animal" is not contradicted by "If Toto is a dog wearing a collar, then Toto is an animal." These are statements about logical implication.

That does not mean that 3 = 3 + 1. That is just idiotic.

I suggest that you put your mind to learning what the meaning of the symbols in algebra means in algebra rather than trying to build some isomorphism between logic and elementary algebra.

• topsquark

##### Full Member
That's so wrong.

Why do you argue about given information? You were told that some quantity (represented by symbol x) is always twice as big as some other quantity (represented by symbol y). Why can't you accept that information as given? because I concluded that and "not" directly give me that! .. my point isn't that I'm not accepting that, my point is that we get that not directly as "given" ! I mean none give me that in advance..

#### Ryan\$

##### Full Member
That's so wrong.

Why do you argue about given information? You were told that some quantity (represented by symbol x) is always twice as big as some other quantity (represented by symbol y). Why can't you accept that information as given? "You were told that some" who told that? that's my point .. Yeah I concluded that from the equation after I did analysis but it wasn't directly given .. so still I consider it as "given" .. if so ..how is that true or reasonable? can you give me please a more real life analogy that imply the truth of that?