Math help

Test Preparation SAT Preparation
1

<p>{(-2)^3 * 8^2} = (2^4)^n</p>

<p>Find the value of n</p>

<p>A - 6
B - 7
C - 8
D - 9
E - 10</p>

<p>Can anyone explain how I go on about doing this?</p>

2

<p>Why not ask Dr. Chung? ;)</p>

3

<p>Well this is a matter of bases and exponents. If 2^x=2^3 then x=3. If the bases are hte same then the exponents must be equal.</p>

<p>The left side becomes -512 or 2^(-9)
The right side is 16^n or 2^4n </p>

<p>So 4n=-9 and n=-9/4…but that’s not one of the answer choices???</p>

4

<p>For this problem I would just use your calculator together with the basic strategy of “starting with choice (C)” as your first guess.</p>

<p>Putting the left hand side in your calculator gives -512.</p>

<p>But the right hand side must be positive. So you must have copied the question incorrectly.</p>

5

<p>It should be
{(-2)^3 * 8^2}^4 = (2^4)^n</p>

<p>Find the positive value of n</p>

<p>A 6
B 7
C 8
D 9
E 10</p>

<p>PS Start here 8^2 is 2^?</p>

6

<p>

</p>

<p><a href=“http://okayface.com/okay-face.jpg[/url]”>http://okayface.com/okay-face.jpg&lt;/a&gt;&lt;/p&gt;

<p>

</p>

<p>2^6</p>

<p>But I don’t see why he put it as (2^3)^2</p>

<p>Why not just 2^6?</p>

<p>Also, what is an easy way to find alternatives to a exponent. For example, I had to individually do 2^4, 2^5, 2^6 till I found that 2^6 was equivalent to 8^2.</p>

<p>Is there a faster way to do that?</p>

7

<p>

</p>

<p>I assume that Chung did that to show that (2^3) = 8 and that he believes (correctly) that all SAT takers would see why he wanted to keep it in the form 2^x. And, yes, the result is 2^6 but this was easier to see by looking at (2^3)^2 than through force computing. </p>

<p>

</p>

<p>You should not have to do this. Compare to what you did and look at solving (2^3)^2. </p>

<p>May I suggest you review the basic rules of exponents until you become very familiar with the operations.</p>

<p>PS Perhaps you do understand the basic rules, and I may be confused by your question. Do you understand the problem once you have the form {(-2)^3 * 2^6}^4 = (2^4)^n or (-2)^12 * 2^24 = (2^4)^n ?</p>

8

<p>Yeah, exponents are pretty hard for me, I will review them. </p>

<p>

Facepalm… Wow, I can’t believe I couldn’t see that. Seems like I have to go back to base 1 in exponents :(</p>

<p>Thanks a ton though, xiggi :)</p>

9

<p>It’s better to find out you need a quick revision during practice than on a real test. Do not feel bad; this is the stuff we all understand when learning it and quickly forget. After all, how many times do we need to play with exponents in this fashion? </p>

<p>For this problem, make sure you see why (and where) you could add exponents or multiply them. Compare left and right side of equation below: </p>

<p>(-2)^12 * 2^24 = (2^4)^n</p>

<p>Once you refresh your memory, it will stick for a long time. :)</p>

10

<p>

</p>

<p>Yeah I understand this. You would have to multiply the outside exponents to the ones inside the “( )”. So you would get (-2)^12 * 2^24 = (2^4)^n. (-2)^12 is the same as 2^12, so you can add the exponents to become 2^36 = (2^4)^n. Then 2^4*9 = 2^36.</p>

<p>It was mostly because I didn’t understand the first part :frowning: </p>

<p>I will have to review/check exponents. I am very shaky on it. Thanks for you help though.</p>