limit (x^2 - root x) / (root x - 1)
x--->1
= limit root x ( x^3/2 -1) / (root x - 1)
x--->1
= limit root x X limit (x^3/2 - 1) / (root x - 1)
x--->1 x--->1
= 1^1/2 X 3/2 X 1^(3/2 - 1)
[since limit (x^n -a^n) / (x-a) = n*a^(n-1) ]
x--->a
=1 X 3/2 X 1^1/2
=1 X 3/2 X 1
=3/2
2007-02-03 23:57:03
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answer #1
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answered by Kristada 2
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Assuming you want to solve
lim [ (x^2 - sqrt(x)) / sqrt(x - 1) ]
x -> 1
One way to solve this without using L'Hospital's rule is to multiply top and bottom by the conjugate of the top. That is, multiply top and bottom by x^2 + sqrt(x). This will give us a difference of squares on the top.
lim [ { (x^2 - sqrt(x))(x^2 + sqrt(x)) } / { (x^2 + sqrt(x)) sqrt(x - 1) } ]
x -> 1
lim [ (x^4 - x) / { (x^2 + sqrt(x)) sqrt(x - 1) } ]
x -> 1
Factoring out a sqrt(x) on the bottom, and an x on the top, we have
lim [ x(x^3 - 1) / { x^(1/2) (x^(3/2) + 1) sqrt(x - 1) } ]
x -> 1
Now we can cancel the x^(1/2) using the x on the top. Note that the x on the top is really x^1, so we can subtract exponents.
lim [ x^(1/2) (x^3 - 1) / { (x^(3/2) + 1) sqrt(x - 1) } ]
x -> 1
Let us also multiply top and bottom by sqrt(x - 1), to eliminate the radical on the bottom.
lim [ { x^(1/2) (x^3 - 1)sqrt(x - 1) } / { (x^(3/2) + 1) (x - 1) } ]
x -> 1
Now, we can factor x^3 - 1 as a difference of cubes.
lim [ { x^(1/2) (x - 1)(x^2 + x + 1)sqrt(x - 1) } / { (x^(3/2) + 1) (x - 1) } ]
x -> 1
And now, we can cancel out the (x - 1) term.
lim [ { x^(1/2) (x^2 + x + 1)sqrt(x - 1) } / { (x^(3/2) + 1) } ]
x -> 1
At this point, we can safely plug in the point x = 1, to give us
{ (1)^(1/2) (1^2 + 1 + 1)sqrt(1 - 1) } / { 1^(3/2) + 1 }
We can already see that sqrt(1 - 1) automatically gives us 0, so we get 0/2, which is equal to 0.
Therefore, our answer is 0.
2007-02-04 00:32:03
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answer #2
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answered by Puggy 7
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Lt x tends to 1 x^2-sqrt x/sqrt x-1
=Lt x tends to 1 x(x-1)/sqrt x-1
=Lt x tends to 1 x(sqrt x-1*sqrt x+1)/sqrtx-1
=Lt x tends to 1 x(sqrt x+1)
PUT THE VALUE 1 IN X,
=1*sqrt2=sqrt2
Best of luck for the exams
2007-02-04 02:35:58
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answer #3
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answered by Anonymous
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If we put x=1 in the original function, it becomes 0/0, hence we can apply L'hospital rule
lim x->1 (x^2 - x^(0.5))/(x^(0.5) -1)
= lim x->1 (2*x - 0.5* *x^(-0.5))/(0.5 * x ^ (-0.5))
= (2 - 0.5)/0.5 (applying x =1 now as it is not 0/0 or y/0)
= 1.5/0.5
= 3
2007-02-04 00:17:36
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answer #4
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answered by voodoochap 1
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What does "sen" recommend? Do you recommend "sin"? i'm fairly constructive the reply is infinity, because the utmost degree contained in the numerator is two, even as the utmost degree contained in the denominator is a million (because the x² contained in the denominator is below an intensive, its degree is merely a million).
2016-11-02 07:00:32
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answer #5
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answered by Anonymous
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using l hospital rule , we get
0
2007-02-03 23:54:32
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answer #6
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answered by Anonymous
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