# Did I need to rationalise the denominator?

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Hi, I was given this question.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

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#2

(Original post by

Hi, I was given this question.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

**nicevans1**)Hi, I was given this question.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

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#3

**nicevans1**)

Hi, I was given this question.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

eg.

Then at this point you would rationalise the denominator.

The alternative is to rationalise first which is probably the easier method.

And no, you cannot anticipate a whole number answer because it isn't.

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Thanks for the replies.

I made a mistake with my equation or "how I wrote it". The denominators are the square root of 2 then minus 1 and the other one is the square root of 2.

Anyway this equation will definitely equal 3... lol

1) So just to confirm in one way or another you would have to rationalise the denominator at some point?

2) You could not tell just from looking at this "new" equation that it would equal a whole number?

Thanks again

I made a mistake with my equation or "how I wrote it". The denominators are the square root of 2 then minus 1 and the other one is the square root of 2.

Anyway this equation will definitely equal 3... lol

1) So just to confirm in one way or another you would have to rationalise the denominator at some point?

2) You could not tell just from looking at this "new" equation that it would equal a whole number?

Thanks again

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#5

**nicevans1**)

Hi, I was given this question.

3 / (2root2 - 1) - 6 / (2root2)

I rationalised the denominators and the final answer is 3. I have 2 questions.

1 )Could I have completed this question without rationalising the denominators?

2) By looking at this question first, is there anyway I could of know that the final answer would be a whole number?

Thanks for either answers.

No rationalising needed

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Hi thanks for the reply.

does this not contradict the reply of the other poster that at somepoint you need to rationalise the denominator?

does this not contradict the reply of the other poster that at somepoint you need to rationalise the denominator?

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#7

(Original post by

Hi thanks for the reply.

does this not contradict the reply of the other poster that at somepoint you need to rationalise the denominator?

**nicevans1**)Hi thanks for the reply.

does this not contradict the reply of the other poster that at somepoint you need to rationalise the denominator?

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Yes im waiting for someone to respond to my changed question. Your answer was to the original question, was it not?

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#9

(Original post by

Yes im waiting for someone to respond to my changed question. Your answer was to the original question, was it not?

**nicevans1**)Yes im waiting for someone to respond to my changed question. Your answer was to the original question, was it not?

I posted after you changed the question ... I was answering the correct question ... The one where the answer is rational so there is no need to rationalise the denominator

Please use the reply button

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ok. I would like to change my post/question one more time... If I had NEVER told you the answer would of been 3 (a rational number)...

1) would you of then had to reationalise the denominator?

Many thanks.

p.s when you say the reply button? there are 3. I automatically go to quick reply...

1) would you of then had to reationalise the denominator?

Many thanks.

p.s when you say the reply button? there are 3. I automatically go to quick reply...

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#11

(Original post by

ok. I would like to change my post/question one more time... If I had NEVER told you the answer

1)

Many thanks.

p.s when you say the reply button? there are 3. I automatically go to quick reply...

**nicevans1**)ok. I would like to change my post/question one more time... If I had NEVER told you the answer

**would of**been 3 (a rational number)...1)

**would you of**then had to reationalise the denominator?Many thanks.

p.s when you say the reply button? there are 3. I automatically go to quick reply...

No, you don't need to rationalise the denominator(s).

The Reply button is the first one you come to, the one next to the double quote (") icon - it causes the previous poster's text to be quoted so they can see you have replied to them (as I have done here)

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#12

**nicevans1**)

ok. I would like to change my post/question one more time... If I had NEVER told you the answer would of been 3 (a rational number)...

1) would you of then had to reationalise the denominator?

Many thanks.

p.s when you say the reply button? there are 3. I automatically go to quick reply...

The reply button that is on the post you with to reply to .... This tells the poster that you have replied

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(Original post by

"would have" not "would of"

No, you don't need to rationalise the denominator(s).

The Reply button is the first one you come to, the one next to the double quote (") icon - it causes the previous poster's text to be quoted so they can see you have replied to them (as I have done here)

**davros**)"would have" not "would of"

No, you don't need to rationalise the denominator(s).

The Reply button is the first one you come to, the one next to the double quote (") icon - it causes the previous poster's text to be quoted so they can see you have replied to them (as I have done here)

(Original post by

No I would not have rationalised .... I would add the fractions and the answer would have factorised and cancelled

The reply button that is on the post you with to reply to .... This tells the poster that you have replied

**TenOfThem**)No I would not have rationalised .... I would add the fractions and the answer would have factorised and cancelled

The reply button that is on the post you with to reply to .... This tells the poster that you have replied

ok - but i'm guessing it's easier to rationalise the denominator as this question was one that was given in the section in my book about the rationalising?

And just so i know, is this the right way to do it your way and to make the denominators the same?

3(root2) - 6(root2-1) / root2-1 * root2

3root2 -6root2-6 / 2-root2

Right so far and if so where next?

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#14

(Original post by

lol - i love learning new things :-)

ok - but i'm guessing it's easier to rationalise the denominator as this question was one that was given in the section in my book about the rationalising?

And just so i know, is this the right way to do it your way and to make the denominators the same?

3(root2) - 6(root2-1) / root2-1 * root2

3root2 -6root2-6 / 2-root2

Right so far and if so where next?

**nicevans1**)lol - i love learning new things :-)

ok - but i'm guessing it's easier to rationalise the denominator as this question was one that was given in the section in my book about the rationalising?

And just so i know, is this the right way to do it your way and to make the denominators the same?

3(root2) - 6(root2-1) / root2-1 * root2

3root2 -6root2-6 / 2-root2

Right so far and if so where next?

Your -6 at the end of the numerator should be a +6 - it comes from -6 x -1.

You can then simplify the numerator by combining the first two terms.

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#15

**nicevans1**)

lol - i love learning new things :-)

ok - but i'm guessing it's easier to rationalise the denominator as this question was one that was given in the section in my book about the rationalising?

And just so i know, is this the right way to do it your way and to make the denominators the same?

3(root2) - 6(root2-1) / root2-1 * root2

3root2 -6root2-6 / 2-root2

Right so far and if so where next?

Second ... How many root2 do you have

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(Original post by

Your -6 at the end of the numerator should be a +6 - it comes from -6 x -1.

**davros**)Your -6 at the end of the numerator should be a +6 - it comes from -6 x -1.

Question is...

3/(root2-1) - 6/(root2)

3(root2) - 6(root2-1) / (root2-1 * root2)

(3*root2 - 6root2+6) / ( 2-root2)

(6-3*root2) / (2-root2)

Good so far? Im unsure from here. Another clue maybe?

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#17

(Original post by

Rushing.!!!

Where about? Ive continued below...

Question is...

3/(root2-1) - 6/(root2)

3(root2) - 6(root2-1) / (root2-1 * root2)

(3*root2 - 6root2+6) / ( 2-root2)

(6-3*root2) / (2-root2)

Good so far? Im unsure from here. Another clue maybe?

**nicevans1**)Rushing.!!!

Where about? Ive continued below...

Question is...

3/(root2-1) - 6/(root2)

3(root2) - 6(root2-1) / (root2-1 * root2)

(3*root2 - 6root2+6) / ( 2-root2)

(6-3*root2) / (2-root2)

Good so far? Im unsure from here. Another clue maybe?

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(Original post by

Factorise the numerator

**TenOfThem**)Factorise the numerator

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