Just read about Godel. If you don't understand it, that's your failing.
The rules of algebra are rules of reality. 2 apples + 2 apples = 4 apples. By the same completely realistic reasoning, 2x + 2x = 4x. In other words, 2 x's + 2 x's = 4 x's. 2 of anything plus 2 of that same thing equals 4 of that thing. That was true before there were humans. It is not some crazy idea somebody had for the purpose of writing a fiction story. There are completely legitimate reasons we use the systems we use. We use them because they are factual and logical. It is not a mere art project.
Then what about the true algebraic facts that you can't work out with algabraic rules?
The 'obvious' rules of arithmetic often don't apply on the quantum scale, for example. They're only obvious because the only things we've ever experienced are those in immediate experience.
The quadratic formula was discovered, not invented. The value of x in your equation is
-b +/- square root of (b squared - 4ac)
2a
That is in fact the value of x, not something some person decided would be neat to merely call the value of x. If the quadratic formula were just some crazy thing somebody decided to invent and do strange things with, it would have been much easier to make it x = a + b + c. There was no choice on the matter. The quadratic formula is what it is, and there is nothing we can do about it even though we can invent a new language.
That is pretty much exactly what I said so I don't really know what you're going on about. Like I just said, you just solve ax2 + bx + c. You do understand how to do that, right..?
It was something which was 'discovered' in a system with particular rules - rules which were invented. The rules are those of Peano arithmetic, which include,
1. ∀x, y, z ∈ N. (x + y) + z = x + (y + z), i.e., addition is associative.
2. ∀x, y ∈ N. x + y = y + x, i.e., addition is commutative.
3. ∀x, y, z ∈ N. (x · y) · z = x · (y · z), i.e., multiplication is associative.
4. ∀x, y ∈ N. x · y = y · x, i.e., multiplication is commutative.
5. ∀x, y, z ∈ N. x · (y + z) = (x · y) + (x · z), i.e., the distributive law.
6. ∀x ∈ N. x + 0 = x ∧ x · 0 = 0, i.e., zero is the identity element for addition
7. ∀x ∈ N. x · 1 = x, i.e., one is the identity element for multiplication.
8. ∀x, y, z ∈ N. x < y ∧ y < z ⊃ x < z, i.e., the '<' operator is transitive.
9. ∀x ∈ N. ¬ (x < x), i.e., the '<' operator is not reflexive.
10. ∀x, y ∈ N. x < y ∨ x = y ∨ x > y.
11. ∀x, y, z ∈ N. x < y ⊃ x + z < y + z.
12. ∀x, y, z ∈ N. 0 < z ∧ x < y ⊃ x · z < y · z.
13. ∀x, y ∈ N. x < y ⊃ ∃z ∈ N. x + z = y.
14. 0 < 1 ∧ ∀x ∈ N. x > 0 ⊃ x ≥ 1..
15. ∀x ∈ N. x ≥ 0.
There are plenty of systems which use contradictory or separate axioms.
And as I keep trying to communicate to you, there are many true facts about arithmetic which can't be proved in the above system. So your 'obvious facts' are really completely arbitrary and limited.
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