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# Core 1 - Questions involving "Square root" Watch

1. Question 1: Express as a fraction

= =

But why is the mark scheme giving the answer as ? Am I just being being pedantic or am I mathematically incorrect and would be penalised for this?

Question 2: Find the gradient of the curve at the point where

Let

But why is it on the mark scheme they are only looking for ?

I'm so confused now when I'm supposed to take the or . I just don't want to get penalised for putting down two answers when there should only be one.

Thank you very much, I'm looking forward to any advice Good luck with your exams everyone!

Solution to the Square root issue
So, as far as I understand from these comments, if you've been asked to find the then you leave it as a positive answer (since they would have asked you if they wanted both values). But when you are trying to solve something such as then you're answer would be . So basically, always take unless you've been given the square root initially (with the addition/subtraction symbol before it).

Another way of thinking about it: If the was always then it would make putting obsolete since they could have just put or even .
2. (Original post by BobGreggary)
Question 1: Express as a fraction

= =

But why is the mark scheme giving the answer as ? Am I just being being pedantic or am I mathematically incorrect and would be penalised for this?
The mark scheme answer is correct.

If you have, , then the answer is,

But when you have a square root, then you don't need to add plus minus. e.g.
3. (Original post by raheem94)
The mark scheme answer is correct.

If you have, , then the answer is,

But when you have a square root, then you don't need to add plus minus. e.g.
I didn't know this! And I'm doing C4! I've always been pedantic about two answers etc. I suppose it makes perfect sense that a function must only map to one value.
4. but if then the answer is
5. (Original post by BobGreggary)
Question 2: Find the gradient of the curve at the point where

Let

But why is it on the mark scheme they are only looking for ?

I'm so confused now when I'm supposed to take the or . I just don't want to get penalised for putting down two answers when there should only be one.

Thank you very much, I'm looking forward to any advice Good luck with your exams everyone!

6. (Original post by elldeegee)
but if then the answer is
Yes

But the reason that you need to put the is because the is only + on its own
7. (Original post by Junaid96)
I didn't know this! And I'm doing C4! I've always been pedantic about two answers etc. I suppose it makes perfect sense that a function must only map to one value.
Are you trolling?

The OP was making this mistake, so i tried to point it out. What's wrong in it?
8. (Original post by TenOfThem)
Yes

But the reason that you need to put the is because the is only + on its own
so if the square root is included in a function then it is no longer ?
9. (Original post by elldeegee)
so if the square root is included in a function then it is no longer ?
needs the if you want to use both values

but the solution to x2 = 4 is because the solution is
10. (Original post by BobGreggary)
Question 1: Express as a fraction

= =

But why is the mark scheme giving the answer as ? Am I just being being pedantic or am I mathematically incorrect and would be penalised for this?
Because the square root of a number is taken to be the positive square root.

The +- situation occurs when solving an equation.
11. (Original post by elldeegee)
so if the square root is included in a function then it is no longer ?
The symbol and the index are defined as being positive.

If you want both roots you need a sign (e.g. the quadratic formula).
12. (Original post by TenOfThem)
needs the if you want to use both values

but the solution to x2 = 4 is because the solution is
So technically, when the teachers were all being cocky in primary school saying
the isn't but , they were wrong :P
13. (Original post by BobGreggary)
So technically, when the teachers were all being cocky in primary school saying
the isn't but , they were wrong :P
Depends what they were saying really
14. (Original post by BobGreggary)
So technically, when the teachers were all being cocky in primary school saying
the isn't but , they were wrong :P
The teacher would probably be saying that , gives,
15. (Original post by BobGreggary)
So technically, when the teachers were all being cocky in primary school saying
the isn't but , they were wrong :P
Either

a) you didn't understand what they were saying

or

b) they didn't understand what they were saying
16. (Original post by Mr M)
Either

a) you didn't understand what they were saying

or

b) they didn't understand what they were saying
or

c) they were just trying to ensure an understanding that (-2) squared is also 4
17. NB

If the same Primary Teacher told you that you can only take a little number from a big number then .... believe nothing they ever told you
18. (Original post by TenOfThem)
NB

If the same Primary Teacher told you that you cannot take a little number from a big number then .... believe nothing they ever told you
Not sure who is more confused. You or the Primary Teacher.
19. (Original post by raheem94)
Are you trolling?

The OP was making this mistake, so i tried to point it out. What's wrong in it?
I'm not trolling

I genuinely would have put two solutions and would have been baffled if I'd seen the mark scheme.
20. (Original post by Junaid96)
I'm not trolling

I genuinely would have put two solutions and would have been baffled if I'd seen the mark scheme.
I am surprised, i thought most students will know this.

Updated: May 16, 2012
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