[FPL67]

Hi,

what is the domain of ( - x) ^1/4 ?

i thought it must be [0,infinity) but could there be other values that it cannot be?

also can i simplify this? maybe then i could see any other values

Thanks

[Glutamic Acid]

Well, yes, try and factorize x^3 - x, and can you see where it is undefined (i.e. x^3 - x < 0)?

[nuodai]

Your answer's not quite right, but almost.

The function has the domain . Here, , so . Solving this inequality for will give you the domain of the function.

Spoiler:

Factorise and draw a graph -- the function is defined in the regions where the graph is above the x-axis (i.e. is positive).

[around]

Can you factorise x^3-x? Does this help to see when you can't take a fourth root?

[Totally Tom]

looks like lolbridge has a 9am on a wednesday morning...

[Glutamic Acid]

We're all in lectures posting from our (i)phones.

[around]

Originally Posted by Totally Tom

looks like lolbridge has a 9am on a wednesday morning...

they're actually teaching us how to count from 0 to infinity. can you believe that?

[FPL67]

i dont understand, if i factorise it i get x ( - x) >(or equal to) 0 ? so x>0, x>1 (or equal to in both cases.)

so then i can take the fourth root for all x>0

[Totally Tom]

Originally Posted by around

they're actually teaching us how to count from 0 to infinity. can you believe that?

sux to be you.

[Totally Tom]

Originally Posted by FPL67

i dont understand, if i factorise it i get x ( - x) >(or equal to) 0 ? so x>0, x>1 (or equal to in both cases.)

so then i can take the fourth root for all x>0

you've done factorised it wrong.

[FPL67]

oh yeah sorry, so it is x(x^2 -1) > 0
so x>0, x>1, x>-1 ? so my domain would be [-1,infinity)

(please note all > should be greater that or equal to signs)

[nuodai]

Originally Posted by Totally Tom

looks like lolbridge has a 9am on a wednesday morning...

10-12am Monday-Saturday This term at least.

"Lolbridge" is poor; at least call it "Lamebridge" or something

[john !!]

domain is whatever you want, if x = -4, -60 still has 4th roots!

badly posed question =)