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- Thread starter goosey00
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- Mar 1, 2012

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f(b) means evaluate f(x) at the value b. In this case f(3) means find f(x) when x=3.If you have f(x)=a^x and f(3)=64 what does f(2)=? Am I over thinking this one? Is it just f(2)=64 also?

Since you have the constant $a$ you can find it's value from f(3) [64 is a cube number so $a$ is a whole number] as an intermediate step. You won't need a calculator for this one but as a hint $64 = 4^3$

- Solve $f(3)$ in terms of $a$ by substituting $x=3$ in $f(x)=a^x$
- Work out the value of $a$ from the above since you're told that f(3) = 64
- Use that value of $a$ to find $f(2) $ by substituting $x=2$

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- Jan 29, 2012

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An equivalent way to do this would be to note that [tex]a^2= (a^3)^{2/3}= 64^{2/3}[/tex].

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