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#1 2006-12-22 04:57:13

Neha
Member
Registered: 2006-10-11
Posts: 173

solve help please tryed many ways..all came out wrong

Sqrt( 6x - 2)  -  sqrt(9) = 5


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#2 2006-12-22 05:05:45

Devantè
Real Member
Registered: 2006-07-14
Posts: 6,400

Re: solve help please tryed many ways..all came out wrong

Well, first try simplifying it.

√(6x-2) - √9 = 5
√(6x-2) - 3 = 5
√(6x-2) = 8
We know that √64 = 8
So √(66-2) = 8

x = 11

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#3 2006-12-22 05:10:34

Toast
Real Member
Registered: 2006-10-08
Posts: 1,321

Re: solve help please tryed many ways..all came out wrong

Hmmm, that last bit's a bit confusing, I would write it out fully:
√(6x-2) = 8 
6x-2 = 64       [square both sides
6x = 66
∴x = 11

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#4 2006-12-22 05:12:02

Devantè
Real Member
Registered: 2006-07-14
Posts: 6,400

Re: solve help please tryed many ways..all came out wrong

I somehow doubt squaring both sides here would be useful to be honest, it's just down to recognising squares. hmm

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#5 2006-12-22 05:18:15

Neha
Member
Registered: 2006-10-11
Posts: 173

Re: solve help please tryed many ways..all came out wrong

that wht i had also......
but its wrong
why
if u put in 11...
6 * 11 =66
66 - 2 = 64
sqrt64 = 8

then  ohhhhhhhhhhhhhhhhhhhhh myyyyyy god
lol u know hwt i did
i did teh same thing that you all did but at teh end i said sqr8 - sqrt9 lol
ohhhhh my god
thanks guys smile


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#6 2006-12-22 05:20:03

Devantè
Real Member
Registered: 2006-07-14
Posts: 6,400

Re: solve help please tryed many ways..all came out wrong

No problem, Neha.

Feel free to ask away.

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#7 2006-12-22 07:07:29

Toast
Real Member
Registered: 2006-10-08
Posts: 1,321

Re: solve help please tryed many ways..all came out wrong

Devanté wrote:

I somehow doubt squaring both sides here would be useful to be honest, it's just down to recognising squares. hmm

I've never learnt that method before, it sounds strange

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#8 2006-12-22 07:16:10

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: solve help please tryed many ways..all came out wrong

It's practically the same as squaring both sides, really. He's just not saying so, and skipping a few steps. That's fine for relatively simple problems like this, but if you tried that with a more complicated problem then you might confuse yourself.

Your way is pretty much the same as his, but clearer and with more intermediate steps.


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It wanted to be normal.

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