Maths Question??? (1 Viewer)

[ratcher0071]

if x = 3 + sqrt2 , make x - (1/x) have a rational denominator?

SUB it in:
3+sqrt2 - (1/3+sqrt2)

...

and then??

 

[minijumbuk]

It's called rationalising. You should've done this in year 10... No offense, but this is very basic stuff =O basic knowledge expected out of a 3u student.

Times top and bottom by (3-√2).

3+ √2 - 1/(3 + √2) = 3 + √2 - 1(3-√2)/(3+√2)(3-√2)
= 3 + √2 - (3-√2)/(3-2)
= 3 + √2 - 3 + √2
= 2√2

 

[ratcher0071]

It's called rationalising. You should've done this in year 10... No offense, but this is very basic stuff =O basic knowledge expected out of a 3u student.

Times top and bottom by (3-√2).

3+ √2 - 1/(3 + √2) = 3 + √2 - 1(3-√2)/(3+√2)(3-√2)
= 3 + √2 - (3-√2)/(3-2)
= 3 + √2 - 3 + √2
= 2√2

I just thought you times the 3+sqrt2 at the front by 3-sqrt2.
I got confused! :angry:

 

[ratcher0071]

It's called rationalising. You should've done this in year 10... No offense, but this is very basic stuff =O basic knowledge expected out of a 3u student.

Times top and bottom by (3-√2).

3+ √2 - 1/(3 + √2) = 3 + √2 - 1(3-√2)/(3+√2)(3-√2)
= 3 + √2 - (3-√2)/(3-2)
= 3 + √2 - 3 + √2
= 2√2

(3+√2) - (1/3+√2) = 4.187672643
2√2 = 2.828427125

???

 

[lyounamu]

if x = 3 + sqrt2 , make x - (1/x) have a rational denominator?

SUB it in:
3+sqrt2 - (1/3+sqrt2)

...

and then??

3+ SR(2) - 1/(3+SR(2) = 3 + SR(2) - (3-SR(2))/(3+SR(2))(3-SR(2))
= 3 + SR(2) - (3-SR(2))/7
There you go

 

[ratcher0071]

3+ SR(2) - 1/(3+SR(2) = 3 + SR(2) - (3-SR(2))/(3+SR(2))(3-SR(2))
= 3 + SR(2) - (3-SR(2))/7
There you go

how about if x=√3 + 2 (same question)

 

[lyounamu]

how about if x=√3 + 2 (same question)

Ok,

Then x - 1/x = SR(3) + 2 - 1/(SR(3)+2)
= SR(3) + 2 - (SR(3)-2)/(SR(3)+2)(SR(3)-2)
= SR(3) + 2 - (SR(3)-2)/-1
= 2SR(3)

 

[clintmyster]

you know when you do these questions, do you do it on a piece of paper first then post or just do it here?

 

[ratcher0071]

you know when you do these questions, do you do it on a piece of paper first then post or just do it here?

yeah

 

[lyounamu]

you know when you do these questions, do you do it on a piece of paper first then post or just do it here?

No, I just write it straight here.

I cannot be bothered trying to find my non-existent pen in my room. And I have to use computer's calculator since I don't have calculator here.

 

[ratcher0071]

Soz, another question. Namu, you must be like :mad1:

Factorise fully:
a²-b²+2a-2b

so far i got:
(a-b)(a+b)+2(a-b)
CAN you factorise any further?

 

[kaz1]

if x = 3 + sqrt2 , make x - (1/x) have a rational denominator?

SUB it in:
3+sqrt2 - (1/3+sqrt2)

...

and then??

Lol
That exact question was in my 2unit exam.

 

[clintmyster]

id take a guess and factor out the a-b but thats just cos its too simple of a question if you just leave it wid ur answer

 

[lyounamu]

Soz, another question. Namu, you must be like :mad1:

Factorise fully:
a²-b²+2a-2b

so far i got:
(a-b)(a+b)+2(a-b)
CAN you factorise any further?

Yeah,

(a-b)(a+b) + 2(a-b) = (a+b+2)(a-b)

 

[kaz1]

Soz, another question. Namu, you must be like :mad1:

Factorise fully:
a²-b²+2a-2b

so far i got:
(a-b)(a+b)+2(a-b)
CAN you factorise any further?

So was that one.

You can factorize it down to (a+b+2)(a-b).