I forgot how to solve for an exponent

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Homework Help Overview

The discussion revolves around solving for the exponent \( b \) in the function \( f(x) = a \cdot x^b \) using given function values at specific points. The original poster expresses uncertainty about how to set up the equations based on the provided values \( f(1.5) = 10 \) and \( f(1.7) = 14 \).

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster considers whether to set the function values equal to each other and questions the validity of this approach. Another participant suggests plugging in the known values to create two equations, leading to a relationship between \( a \) and \( b \). There is also a mention of using logarithms to solve for \( b \).

Discussion Status

The discussion is active, with participants exploring different interpretations of how to approach the problem. Guidance has been provided regarding setting up equations based on the function values, and there is acknowledgment of the algebraic steps involved.

Contextual Notes

Participants are working within the constraints of needing to solve for two unknowns with two equations, and there is an underlying uncertainty about the correct method to apply.

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Homework Statement


i need to solve for b in f(x)=a*xb
i know f(1.5)=10 and f(1.7)=14

it's been forever since i did calc like this and i am blank on what to do.
i can't remember if or how i can set them equal to each other to solve for b.
i know i have 2 eqns and 2 unknowns.

do i set f(1.5)=f(1.7)? i don't think that's right but i can't think of what else to do??
 
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bocobuff said:

Homework Statement


i need to solve for b in f(x)=a*xb
i know f(1.5)=10 and f(1.7)=14

it's been forever since i did calc like this and i am blank on what to do.
i can't remember if or how i can set them equal to each other to solve for b.
i know i have 2 eqns and 2 unknowns.

do i set f(1.5)=f(1.7)? i don't think that's right but i can't think of what else to do??

Why would you set them equal to each other? You know they equal 10 and 14 respectively so are you saying 10 = 14?

What you should do is plug it in, i.e. f(1.5) = a*1.5^b = 10 then do the same with the other point, now you will have 2 equations and 2 unknowns, so for example a = 10/1.5^b, figure out what a = in the other equation and set THOSE equal to each other.
 
alright I'm an idiot.
so you get something like 14/10=(1.7/1.5)^b and then take natural log of each side right...?
 
Assuming your algebra is correct, yes.
 
sweet thanks a lot
 

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