amitjash wrote:
If 3^6x = 8,100, what is the value of (3^x – 1)^3 ?
A. 90
B. 30
C. 10
D. 10/3
E. 10/9
Please when posting such questions make sure that it's not ambiguous.
Correct question is: If 3^(6x) = 8,100, what is the value of [3^(x-1)]^3?
Or it can be written using the formating as: If \(3^{6x}=8,100\), what is the value of \((3^{x-1})^3\)? (It's not hard at all).
\(3^{6x}=(3^{3x})^2=90^2=8,100\) --> \(3^{3x}=90\).
\((3^{x-1})^3= 3^{3x-3}=\frac{3^{3x}}{3^3}=\frac{90}{27}=\frac{10}{3}\).
Answer: D.
Check Number Theory chapter of Math Book for exponents (link in my signature).
Please point out the mistake in this approach. Why am I not getting correct answer by this method.
Now, 3^(3*(x-1)) = 3^(3*(-1/3)) = 3^(-1) = 1/3.