Anonymous
Anonymous asked in Science & MathematicsMathematics · 7 years ago

Am I wrong, or is it the book?

(3^-n . 9^2n) / (3^[3n-2] . 27)

This simplifies first to (3^-n . 3^4n) / (3^[3n-2] . 3^3). Call this step 1.

Now, if I use the laws of indices to work it out straight from step 1, I get

3^(-n + 4n - [3n - 2] - 3) Step 2

= 3^-1

= 1/3

The book gives the answer answer as 1/243, which is 3^-5. That would be correct if, from step 2, I SUBTRACT the 2. I added it because it's subtraction of a negative number. Am I correct, or have I missed something in working out the indices?

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  • 7 years ago
    Favourite answer

    One easy way to disprove the result of the book is to set n = o. as n plays no roll in the final answer you can choose it to be anything you want. n = 0 makes the numerator = 1 and the denominator = 3.

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