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C1 Maths

What is the answer to 16/9 ^ 1/2? Is it + 4/3 and - 4/3????
Original post by Qwerty11999999
What is the answer to 16/9 ^ 1/2? Is it + 4/3 and - 4/3????


Just +4/3.
it's 4/3
Original post by zayn008
You're absolutely correct :smile:


So is it the + and - answer. Keep getting confused.
Original post by Qwerty11999999
So is it the + and - answer. Keep getting confused.


Refer to my answer.

Original post by RDKGames
Just +4/3.
Original post by RDKGames
Refer to my answer.


Oh ok thanks, i was just wondering because (-4/3)^2 = 16/9. So therefore there must be a - answer.
Original post by zayn008
Both, because when you square root 4 for example you can have 2 but if you square -2 (-2 * -2) you'll get positive 4 as well so there's 2 possibities and you must list both or you'll lose an easy mark! Technically you'd say 'Or' rather than 'and'. They like doing this in C1 with rearrangement questions, I would write it as +/- 4/3


Thanks and yes thats exactly how i wrote out my answer. Cheers for advice.
Original post by Qwerty11999999
Oh ok thanks, i was just wondering because (-4/3)^2 = 16/9. So therefore there must be a - answer.


Nope.

Here is a graph of y=xy=\sqrt{x}. As you can see, there are no negative y values.

If you had an equation of x2=169x^2=\frac{16}{9} then x=±43x=\pm \frac{4}{3} (-ve and +ve) are both solutions.

SADsad.PNG
Original post by Qwerty11999999
So is it the + and - answer. Keep getting confused.


(169)12=169=43 (\frac{16}{9})^\frac{1}{2} = \sqrt{ \frac{16}{9} } = \frac{4}{3}

When you have the square root, the answer is only the principal solution which is positive. For example, x2=+x \sqrt{x^2} = +x or the mod of x.
(edited 7 years ago)
Original post by Qwerty11999999
Thanks and yes thats exactly how i wrote out my answer. Cheers for advice.


You may find this thread useful :h:
Original post by zayn008
Both, because when you square root 4 for example you can have 2 but if you square -2 (-2 * -2) you'll get positive 4 as well so there's 2 possibities and you must list both or you'll lose an easy mark! Technically you'd say 'Or' rather than 'and'. They like doing this in C1 with rearrangement questions, I would write it as +/- 4/3


Nope nope nope.

http://www.thestudentroom.co.uk/showthread.php?t=4066671&p=64637655#post64637655
Original post by RDKGames


Ok thanks what about 25^ -3/2. What would that be? Just +1/125
Original post by Qwerty11999999
Ok thanks what about 25^ -3/2. What would that be? Just +1/125


Yes.
Reply 13
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3121
21
Original post by RDKGames


Wow thanks I've been doing it wrong all this time. Guess I've never been called out because the mark schemes condone it but it's useful to know, didn't realise you only did +/- with algebrea, cheers 👍🏼
Original post by RDKGames
Yes.


Ok thanks, its just that my book says that you should have a + and - answer.
Original post by Qwerty11999999
Ok thanks, its just that my book says that you should have a + and - answer.


Depends what the question is. If it's only the root of 16/9 by itself then it's just +4/3.

If it's like x2=16/9x^2=16/9 then x=+4/3 and x=-4/3
Reply 16
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Ipsooo
5
It is true that (-4/3)squared takes you back to 16/9 but by convention the square root always refers to the positive part. (Another way to write mod x is square root of x^2, try it on desmos!)

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