Why is $5x+10=2$ not a proposition?
My textbook says, "a proposition is any statement that is true or false and its truth value can be known, unknown, true, false, or a matter of opinion".
By that definition, $5x+10=2$ should be a proposition because the truth value is "unknown".
I'm trying to submit some answers into my online homework software and it's telling me that $5x+10=2$ is not a proposition.
Thanks in advance.
Best Answer
I see where you're coming from, but that is not what the definition means by "unknown". They are thinking of a statement like "Every even integer greater than 4 can be expressed as the sum of two primes". That is definitely either true or false, but we don't know which one.
$5x+2=10$ is a statement whose truth or falsity depends on the value of the variable $x$, so this is a very different situation. I would use the word "predicate" to describe this situation, but your textbook or teacher may have a different idea of how the vocabulary shakes out.