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Find the inverse

 
 
Reply Wed 19 Oct, 2011 12:28 pm
f(x)=2x+1
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Type: Question • Score: 0 • Views: 615 • Replies: 2
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engineer
 
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Reply Wed 19 Oct, 2011 12:34 pm
@jaytee12003,
If you are looking for the inverse function, solve for x in terms of f(x)

y = 2x + 1
y1 = 2x
(y - 1 )/2 = x

So the reverse function is f'(x) = (x-1)/2 (putting the x in for y to put it in the standard form.)
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raprap
 
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Reply Wed 19 Oct, 2011 03:59 pm
@jaytee12003,
Engineer is completely correct.

if f(x)=2x+1

then y=2x+1->2x=y-1->x=(y-1)/2
now substitute x for y
so the inverse f^-1(x)=(x-1)/2

but now check your answer with the property
f o f^-1= f^-1 o f=x

((2x+1)-1)/2=2x/2=x & 2((x-1)/2)+1=(2x-2)/2+1=x-1+1=x

So the inverse is f^-1(x)=(x-1)/2

the rules for finding an inverse of a one to one function are
1) substitute y for f(x)
2) solve for x in terms of y
3) then substitute x for y
4) check your answer

Rap


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