If x is a negative number, then | x | = − x. This is incorrect. It should read "If x is a negative number, then | - x | = x."
The latest change is an error. If x is a negative number, then -x is a positive number! It was correct before, the absolute value of x, where x is negative, is -x: If x is negative, | x | = − x
- I see what you're saying...I think the working just needs to be changed. |-x| = x but if you declare before hand that x is negative to begin with then |x| is negative, but if you say it equals x, x is still assumed negative. Let's just reword the whole thing, shall we? --David B (talk) 20:48, 14 April 2016 (EDT)
- How about simply:
or even show all the signs:
There should not be any signs inside the absolute value bars. That's where we're going off the rails. You should state the range of x, as in "if x is negative" and then show | x |. I know you want to have | -x | mean something like "the absolute value of a negative number" but that's not what it means. It was correct before: "If x is negative, then | x | = -x." You have to think about what it means for a second, but math is like that. MelH (talk) 22:58, 14 April 2016 (EDT)
- I see what you are getting at, but you can have a negative number inside ||, it just translates to positive. You see this in just about ever math textbook. --David B (talk) 00:44, 15 April 2016 (EDT)
- Sure. But your confusing two things. What you see is statements like | -3 | = 3. That's different from, "for negative x, | -x | = ..." The first is an example, and it's clear. The second is confused. The "for negative x" part says that x IS a negative number, like -3. "| -x |" then becomes a positive number, like 3. Examples with negative constants are fine. Examples with variables that have been asserted to represent negative numbers, which are then negated, not fine. MelH (talk) 02:01, 15 April 2016 (EDT)