x + 2 = x - 2
I found x, twice even. EZ
I find this meme and this comment section distressing. Y’all are bad at basic algebra.
Carry on, I guess.
Subtract x from both sides of the equation. You get 2 = -2 which is incorrect and nonsensical.
I know that, but @Urist@lemmy.blahaj.zone said that most of us here are bad at basic algebra. Not that I’m great at it (I had an 8 average in all 4 maths in uni), but I do believe that most of us here were correct. This is unsolvable using classic algebra.
2 = -2, easy
Can someone smart explain it to dumb me
Explanation: How did they get from
x + 2 = x - 2
to
(x+2)(x-2)=0?
That’s not a valid step.
To further clarify,
(x+2)(x-2) means to take the result of X+2 and times it with the result of x-2.
While it is common in algebra to bring the other side over, in order to simplify it, this isn’t how you’d do it.
Here, you’d either cancel out the X (by removing it on both sides) or the -2 (by adding 2 to both sides) over to make 2=-2 or X+4=X respectively, which are both nonsense equations.
they start off with S’ though… looks like they pretended to try to derive?
Almost everything is wrong in his answer.
The correct answer is, it’s unsolvable.
X + 2 = X - 2
X - X = - 2 - 2
0 = - 4
It’s not solvable using traditional algebra.
Typically you would try to get all of the variables on one side, and all of the numbers on the other.
So in this instance, you’d start by moving them around to get things together:
x+2 = x-2
x+2-x = -2
x-x = -2-2
But then you simplify, and cancel out any variables that need to be cancelled. In this case we see “x-x” so that cancels out to 0. And we see -2-2 which simplifies into -4. So the end result is:
0=-4
Which is obviously a nonsense answer. In the original post, homeslice did the first step wrong, moved everything over to the left incorrectly, (inadvertently setting the whole equation equal to 0) and the whole thing was downhill from there; Since the first step of their solution was wrong, everything behind it was also wrong.
You know how you sometimes make a mistake in one line, but after doing a few lines, you go back to actually writing the equation correctly? Happened to me all the time in uni. It’s basically because you were thinking of doing the next line or whatever, and you just forgot that a var or const was somewhere in there, or you just didn’t copy (or copy it correctly) in the next line, but the memory of that var/const remained in your brain, so after doing a few lines, the equation is now simple enough so your brain knows something should be there, but it’s missing. Sure, we almost always caught up with the mistake, go back, correct the last few lines and carry on. But, every once in a while, you don’t, and you carry on solving the equation, and you get a correct solution, but from a purely mathematical standpoint, yes, that solution is not correct.
My math proffesor in uni had an interesting take on this. He said, you didn’t do 1 mistake and then correct it to get the right answer, but you actually made 2… which is worse… according to him. And I have to say, at that time, I didn’t agree, but let’s be honest… he is correct. So, he went a lot harder on those students that did this type of mistake than the ones that just made 1 and carried on solving the equation like nothing happened.
nah… its still just one error: that of transcribing your process.
it’s like a cosmic ray randomly changed a digit in the memory cells that hold the stringbuffer prepared to be printed.
and then the computation carries on with the internal representation of the whole process still with correct data.
i understand your profs pov though
There isn’t a valid answer to the question.
Ignore the numbers, and just think about this:
Is there a number that you can add 2 to, that would equal the same about as if you subtracted 2 from it?
The answer is no.
So the person, who is pretending to be smart, just did a bunch of fake math.
Also √4 = 2, so the “answer” they have is just them trying to re-write the question x + 2 = x - 2.
The square root of x is usually defined as the positive real number that squares to x, so x^2 = 4 => x = ±2 but sqrt(4) = 2, not ±2
The complex sqrt function is multivalued, but that opens a whole other can of worms