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Olden
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#1
Report Thread starter 15 years ago
#1
The function f is given by:

1/(x^2 - 1) where x > 1

a) Find the range of f

The function g is given by:

2/x where x >0

b) Solve gf(x) = 70

I need help on these two questions. How would you go about doing these?
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Juwel
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#2
Report 15 years ago
#2
(Original post by Jubba)
The function f is given by:

1/(x^2 - 1) where x > 1

a) Find the range of f

The function g is given by:

2/x where x >0

b) Solve gf(x) = 70

I need help on these two questions. How would you go about doing these?
The range of f is all possible values that f(x) can take. So in this case f(x) > 0.

gf(x) = 2/(1/x^2-1) = 2(x^2-1)

Set gf(x) = 70,
70 = 2(x^2-1)
35 = x^2-1
34 = x^2
x = sqrt 34
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Silly Sally
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#3
Report 15 years ago
#3
(Original post by ZJuwelH)
The range of f is all possible values that f(x) can take. So in this case f(x) > 0.

gf(x) = 2/(1/x^2-1) = 2(x^2-1)

Set gf(x) = 70,
70 = 2(x^2-1)
35 = x^2-1
34 = x^2
x = sqrt 34
Small mistake: from the line 35 = x^2 - 1

it should then be x^2 = 36, rather than 34
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Juwel
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#4
Report 15 years ago
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(Original post by Silly Sally)
Small mistake: from the line 35 = x^2 - 1

it should then be x^2 = 36, rather than 34
D'oh! Cheers.
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Olden
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#5
Report Thread starter 15 years ago
#5
safe people. nice one.

ZJuwelH i noticed ur located in bethnal green. i liv dere 2. which skool did u go 2?
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