IGCSE Functions Watch

Laith
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#1
Report Thread starter 10 years ago
#1
f : x I-> 2x – 1
g : x I-> , x ≠ 0

(a) Find the value of
(i) f(3),
...............................
(ii) fg(6).
...............................
(b) Express the inverse function f –1 in the form f –1: x �� ...
.............................
(c) (i) Express the composite function gf in the form gf : x �� ...
...............................
(ii) Which value of x must be excluded from the domain of gf ?
x = ........................
(2)

How do I go about this? (the box represents a symbol I-> )

not the first two
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Kolya
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#2
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#2
Well, what have you done yourself?
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Laith
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#3
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#3
I can understand the first two, but I am confused with the symbol I->. Does it mean the same thing as an equals sign?

I can do the exclusion one provided I can do the others. We have always used = rather than I->
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Kolya
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#4
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#4
It roughly means "maps to". For example, f : x \to 2x-1 means that the function f takes a value x and outputs a value of (2x-1). An alternative notation for this is f(x) = 2x-1
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Laith
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#5
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#5
Thanks! Ill relay back the answer and it would be great if you could check it!
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Laith
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#6
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#6
ok here goes:

a) 5
ii) 0
b) (x+1)/2
c) 3/(2x-1)
ii) 1/2
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Kolya
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#7
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#7
Well, you haven't told us what g is, but your answers to a)i. and b) are correct.
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Laith
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#8
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#8
what do you mean?
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Kolya
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#9
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#9
In your first post, you haven't told us what the function g is. This, combined with my lack of supernatural powers, means I cannot check the rest of your answers.
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Laith
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#10
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#10
oh i am extremely sorry

g(x)= 3/x (and cannot equal 0 for obvious reasons)
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walrusgod
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#11
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#11
Your answers look right
0
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Laith
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#12
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#12
thanks very much
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