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Maths problem

 
 
Euler
 
Reply Sat 18 Jun, 2005 10:44 pm
I've got query on the answer of this problem..

y=(1-2x)^(-1/3)
the range of values of x
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Type: Discussion • Score: 1 • Views: 694 • Replies: 4
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raprap
 
  1  
Reply Sun 19 Jun, 2005 07:47 pm
y=(1-2x)^(-1/3)=1/(1-2x)^(1/3)

x cannot be 1/2 (undefined--division by zero)
if x>1/2 then y is negative
if x<1/2 then y is positive
so the range of x is all real numbers except 1/2

Rap
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Euler
 
  1  
Reply Mon 20 Jun, 2005 06:59 am
rap

there's sth you missed out...
the answer is obviously NOT what you've calculated.. i would have no problem on the solution if the answer is that obvious...

the answer is lxl < .5
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engineer
 
  1  
Reply Mon 20 Jun, 2005 08:08 am
Cube root of a negative number
You can take the cube root of a negative number, so I don't see the issue with Rap's answer. If x is 9/16 then 1-2x = -1/8. (-1/8)^(-1/3) = -8 ^(1/3) = -2. You will never get your calculator to pull that off, but it works on paper.
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raprap
 
  1  
Reply Mon 20 Jun, 2005 08:16 am
You wanna 'splain that Lucy.

the cube root of a negative number is a negative number.

Getting my definition problem out of the way, the range of x are all defined x's in the domain of y.
that is
x=1/2-1/2y^3
and the domain of y are real numbers where y<>0
The range of x is expressed as y goes to -0, x goes to +infinity as y goes to -0, x goes to -infinity

Rap
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