Hi,
The answer is D) but I got different answers for 1) and 2)... but I think if the answer is D), both 1) and 2) should have the same number for k...
1) k-1/k=1
k=1/k
therefore k=1??
2) 2k-1=root5
2k=root+1
k=root5/2+1/2
What is the value of k2-k?
(1) The value of k-1/k is 1.
(2) The value of 2k –1 is root5
500 ds test4 #20
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- jayhawk2001
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You don't need the _same_ answer for 1 and 2. It is sufficient if 1 and 2
each yield a unique answer.
Bottom-line you should be able to arrive at a unique value for k^2 - k
using 1 or 2 or both.
each yield a unique answer.
Bottom-line you should be able to arrive at a unique value for k^2 - k
using 1 or 2 or both.
-
- Newbie | Next Rank: 10 Posts
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- Joined: Sat Mar 10, 2007 9:22 pm
No need to calculate the value of k. we can approach the question in a different way
1) k - 1/k =1
multiply with k gives k^2 - 1 =k
now rearraange
K^2-k =1 >>Ans
Now take case 2)
2k-1 = root5
Square the equation ie (2k-1)^2 =5
i.e.
4k^2-4k+1=5
4k^2-4k-4=0 (after re-arranging)
Divide by 4 >> k^2-k-1=0
Re-arranging gives k^2-k=1 >> Ans.
Both cases give the same result ... so Ans is D
1) k - 1/k =1
multiply with k gives k^2 - 1 =k
now rearraange
K^2-k =1 >>Ans
Now take case 2)
2k-1 = root5
Square the equation ie (2k-1)^2 =5
i.e.
4k^2-4k+1=5
4k^2-4k-4=0 (after re-arranging)
Divide by 4 >> k^2-k-1=0
Re-arranging gives k^2-k=1 >> Ans.
Both cases give the same result ... so Ans is D