Core 1 - Questions involving "Square root"

A general exams rule seems to be that when a power is numerically stated, you only need to give the positive answer. If they actually have root9 shown rather than 9 to the half, then you would need to show +or-

At least that's what my teacher has told us...

A general exams rule seems to be that when a power is numerically stated, you only need to give the positive answer. If they actually have root9 shown rather than 9 to the half, then you would need to show +or-

At least that's what my teacher has told us...

Oh dear.

This guy got 100 in both C1 and C2.

I wouldn't worry about it. I saw this guy admit he had no idea about it a couple of weeks ago on twitter. He even tried to argue it was wrong.

http://cambridge.academia.edu/JamesGrime

Why you linked me to this guy? Who is he?

Who admitted, the guy you linked me to or Mr Tough?

The guy I linked you to is a relatively well-known professional maths educator who did not know the definition of the square root.

His videos are here:

http://www.youtube.com/watch?v=V4rRC0bc3xE

He is the singing banana not the dancing badger.

I am surprised, i thought most students will know this.

I'm also surprised I didn't know this :P It's probably because I self-studied and so never had a teacher to tell me.

I also self-studied but i thought this was very common thing to know, so i was surprised.

You should remember that the graph of $y= \sqrt{x}$ doesn't gives any negative values.

Yeah so basically; it's a pretty common mistake and I see it on this forum a lot!

Yeah I used to think the same thing until mid-way through year 12. And this genuinely was from poor clarity from teachers. As was said above by TenOfThem; in early GCSE and year 9 etc. my teacher said things like what's the answer to $x = \sqrt{4}$ and we'd be told off for just saying 2.

In fact, if you scroll back through my posts far enough I think you'll find a thread where Mr. M and nuodai (I think it was them) corrected me on this whole thing.

I don't even think about it now though and know it correctly; but it's easy to run away with incorrect theory if things aren't made clear in earlier teaching (GCSE).

I had to tell my friend about this thing when he did a question wrong just a couple of weeks ago and he's currently on an A in A-level Maths and Physics.



Yeah so basically; it's a pretty common mistake and I see it on this forum a lot!

I will get mad if i try to scroll back through your posts

I really didn't knew that people have confusion on this, when the other guy said he didn't knew it, i thought he is trying to troll.

So your teacher in year 9 wasn't clear about this concept as well, right?

Yeah I used to think the same thing until mid-way through year 12. And this genuinely was from poor clarity from teachers. As was said above by TenOfThem; in early GCSE and year 9 etc. my teacher said things like what's the answer to $x = \sqrt{4}$ and we'd be told off for just saying 2.

WOW! I am on FP2/FP3 and I had no idea, one thing though

$\displaystyle x^2 = 4 \implies \sqrt {x^2} = \sqrt 4$ and $\displaystyle \sqrt 4 = +2$ as the function gives the positive value.

so how come $\displaystyle x = \pm 2$ ?

And if $\displaystyle x^2 = 7$ then would $\displaystyle x = \sqrt7$ or $\displaystyle \pm \sqrt 7$ ?