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Say we have $(x+1)(x+2) = 0$. So possible solutions of $x$ are $x=-1$, and $x=-2$;

Would it be considered correct syntax to say "$x = -1, -2$" ?

blub
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plu
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  • I would write $x=-1\vee x=-2$. – EuklidAlexandria Aug 21 '18 at 22:19
  • Mathematical symbols are shorthand for analogous natural language sentences. I would say: "The values of $x$ that satisfy the equation $(x+1)(x+2)=0$ are $-1$ and $-2$." – wjmolina Aug 21 '18 at 22:26
  • The comma usually means "and". Use an "or" if you want to be precise. In this case however it is "clear from the context". – Bman72 Aug 21 '18 at 22:26
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    You can write $x\in{-1,,-2}$ – Jakobian Aug 21 '18 at 22:27
  • @Cleric In that case, couldn't that have been expressed as "$x = -1 \land -2$"? – plu Aug 21 '18 at 22:27
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    $x = -1 \land -2$ could be read as $x$ is equal to $-1$ and $-2$, which is a contradiction. Mathematics should be written in natural language with symbols as means to simplify otherwise complicated expressions. – wjmolina Aug 21 '18 at 22:31

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Mathematics should be written using natural language with symbols being used as a means to simplify otherwise convoluted expressions or due to conventions. For example:

"If the product of a number times itself plus three times the number plus two is equal to zero, then the number is either negative one or negative two."

is more clearly rewritten as:

"$x^2+3x+2=0$ implies $x=-1$ or $x=-2$".

This should help you view mathematics as a dialogue rather than a programming language of sorts.

wjmolina
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