# Math (Ms. Sue Please Help)

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Determine whether the following statement makes sense or does not make sense, and explain your reasoning (modified from true/false format of text): If

f(x) = 3x, then f^-1 (x) = 1/3x

A) This makes sense because the inverse would divide by 3 to "undo" the multiplication by 3 in f(x).

B) This does not make sense because although we would divide by 3 to "undo" the multiplication by 3 in f(x), the x would appear in the numerator not the denominator.

• Math (Ms. Sue Please Help) - ,

You have to be careful with the term inverse funtion.That is not the same as reciprocal.

if f(x)=3x=y
then the inverse can be found this way:
y=3x
x=3y
y=x/3 or f^-1(x)=x/3

check: inverse(function)must equal x

so f^-1 (f)= 3(x/3)=x so in fact it is the inverse.
So false. Go with B. When dealing with functions, the term "inverse" seldom means reciprocal.

• math - ,

Please help HM

• Math - ,

are u sure about this

• Math (Ms. Sue Please Help) - ,

Christian -- Bobpursley is a math/physics/teacher. HM is probably a high school student.

• Math (Ms. Sue Please Help) - ,

Yes, Christian. But don't trust me. http://www.youtube.com/watch?v=Ec5YYVxyq44 That is the same message.

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