The Student Room Group

Maths: Roots - simplifying

Scroll to see replies

Reply 20
Original post by MrFox
Yes! I understand that part now :smile: hurray , but why does that cancel out?

-6√3+6√3 hmm confuses me I dont get why it cancels out


Consider 1 - 1 = 0

Multiply through by 6√3 (a constant)

(1×63)(1×63)=(0×63)(1\times 6\sqrt3) - (1\times6\sqrt3) = (0\times6\sqrt3)

6363=06\sqrt3 - 6\sqrt3 = 0
Reply 21
Original post by Exon
Consider 1 - 1 = 0

Multiply through by 6√3 (a constant)

(1×63)(1×63)=(0×63)(1\times 6\sqrt3) - (1\times6\sqrt3) = (0\times6\sqrt3)

6363=06\sqrt3 - 6\sqrt3 = 0


Thanks good sir , (yet it still confuses me where the - came from between the 6√3's,) i dont quite understand it yet but thanks for trying. :smile:
Original post by Exon
Consider 1 - 1 = 0

Multiply through by 6√3 (a constant)

(1×63)(1×63)=(0×63)(1\times 6\sqrt3) - (1\times6\sqrt3) = (0\times6\sqrt3)

6363=06\sqrt3 - 6\sqrt3 = 0


There is an invisible 1 after the - sign in the fist place so it's basically -1 x sqrt3. I think, that's what my teacher told me


Posted from TSR Mobile
Reply 23
Original post by Firenze26
There is an invisible 1 after the - sign in the fist place so it's basically -1 x sqrt3. I think, that's what my teacher told me


You quoted the wrong person :colone:
Original post by MrFox
Thanks good sir , (yet it still confuses me where the - came from between the 6√3's,) i dont quite understand it yet but thanks for trying. :smile:

He got the minus from the 1 - 1 = 0 because he multiplied it by 6√3.

Another example might be:
-1 + 1 = 0 or
-2 + 2 = 0 or
-3 + 3 = 0 OR
-6√3 + 6√3 = 0.

Do you see that the 6√3 is seen like a normal integer?
Sorry, needed the formula thing you used, how do you do that anyway?


Posted from TSR Mobile
Reply 26
Original post by Firenze26
Sorry, needed the formula thing you used, how do you do that anyway?


http://www.thestudentroom.co.uk/wiki/latex

Don't worry about it, I thought you clicked the wrong button by accident.
you have to rationalize the denominator = 33/√33 x √33/√33 which equals 33√33/33 which is just √33
Reply 28
Original post by MrFox
Thanks good sir , (yet it still confuses me where the - came from between the 6√3's,) i dont quite understand it yet but thanks for trying. :smile:


Okay, it seems everyone else is failing... drastic measures.

What we have discerned:

36 - 6√3 + 6√3 - 3

If you're OK with this part and how we've gotten it so far, read on. If not, no point in reading on, quote this post and ask how we got there.

Now here comes the radical part: forget about the whole √3 thing for a minute. Let x = √3.

Thus you now have:

36 - 6x + 6x - 3

You should know from the most basic algebra lessons you've had that -6x +6x is equal to 0x. I.e. 0. Thus it all cancels out, and all you need is the 36 - 3 (which, obviously, equals 33). For all intents and purposes, surds can be manipulated in a similar manner to algebraic expressions. This is because, as people have pointed out, surds are treated like any other integers.

Are you any closer to understanding it?
Original post by MrFox
Yes! I understand that part now :smile: hurray , but why does that cancel out?

-6√3+6√3 hmm confuses me I dont get why it cancels out

dude, it cancels out because you have a negative and a positive

for instance: -3 + 3=0 because we have the negative of 3 and we have the positive of 3

now -6√3 + 6√3 = 0 because we have the negative 6√3 and we have the positive 6√3
Reply 30
Original post by NikolaT
Okay, it seems everyone else is failing... drastic measures.

What we have discerned:

36 - 6√3 + 6√3 - 3

If you're OK with this part and how we've gotten it so far, read on. If not, no point in reading on, quote this post and ask how we got there.

Now here comes the radical part: forget about the whole √3 thing for a minute. Let x = √3.

Thus you now have:

36 - 6x + 6x - 3

You should know from the most basic algebra lessons you've had that -6x +6x is equal to 0x. I.e. 0. Thus it all cancels out, and all you need is the 36 - 3 (which, obviously, equals 33). For all intents and purposes, surds can be manipulated in a similar manner to algebraic expressions. This is because, as people have pointed out, surds are treated like any other integers.

Are you any closer to understanding it?


HURRRAAAAY HALLELUJAH. I thank you good sir. and Exos who also helped me finally I understand it! I want to get A for maths so I should be better than this, Im just not in the right state of mind at the moment. Be at rest fellow posters, for I have understood.
Reply 31
Original post by MrFox
HURRRAAAAY HALLELUJAH. I thank you good sir. and Exos who also helped me finally I understand it! I want to get A for maths so I should be better than this, Im just not in the right state of mind at the moment. Be at rest fellow posters, for I have understood.


Glad to be of service, good citizen.

If you need any other maths help, feel free to poke me any time. I got an A* at GCSE and am currently doing A-level maths.

*flies off into the sunset* :cool:
Reply 32
Original post by MrFox
I'm trying to learn Surds but its tricky and way too many roots everywhere, and I'm confused at simplifying.

Here's the question:

Work out: (6+√ 3)(6-√3) / 33
Give your answer in its simplest form.
I've worked out the top part of the equation. 36 - 6√ 3 + 6√ 3 - 3
Now how do I simplify it I'm confused, please tell me how to simplify it.
And any tips on Surds it's really confusing.

Sorry about the title I forgot to put 'Surds' in.


Hi, you've it right so far but all you need to do now is rationalise the denominator.

33/√33= times the bottom and top by √33
This gives you 33√33/33, so the 33s cancel out leaving you with just √33.

Hope this helps:smile:
(edited 10 years ago)

Quick Reply

Latest