assignment 9

course Mth 158

????€?x???z?x??v}?assignment #009009. `query 9

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College Algebra

06-13-2007

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14:47:56

R.9.6. What steps did you follow to simplify (-8)^(-5/3) and what is your result?

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RESPONSE -->

Since the exponent is negative I moved it to the bottom of the fraction. 1/ -8^5/3. -8^5 = -32,768 then I took the cube root and got -32. So my final solution is 1/ -32.

confidence assessment: 2

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14:48:33

** (-8)^(-5/3) = [ (-8)^(1/3) ] ^-5. Since -8^(1/3) is -2 we get

[-2]^-5 = 1 / (-2)^5 = -1/32. **

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RESPONSE -->

I did some things different, but still got the correct answer.

self critique assessment: 3

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14:50:49

R.9.12. What steps did you follow to simplify (8/27)^(-2/3) and what is your result?

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RESPONSE -->

First I took the cube root of 8/27 and got 2/3. Then I sqared 2/3 and got 4/9. Since the 2 was negative I flipped the fraction to get a final answer of 9/4.

confidence assessment: 2

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14:51:20

** Starting with

(8/27)^(-2/3) we can write as

(8^(-2/3)/27^(-2/3)). Writing with positive exponents this becomes

(27^(2/3)/8^(2/3))

27^(2/3) = [ 27^(1/3) ] ^2 = 3^2 = 9 and

8^(2/3) = [ 8^(1/3) ] ^2 = 2^2 = 4 so the result is

(27^(2/3)/8^(2/3)) = 9/4. **

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RESPONSE -->

Again, I did the steps different but still found the correct answer.

self critique assessment: 3

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14:53:08

R.9.24. What steps did you follow to simplify 6^(5/4) / 6^(1/4) and what is your result?

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RESPONSE -->

In this problem, an exponent is being divided by an exponent, so you subtract them to get 6^4/4 which equals 6^1=6.

confidence assessment: 2

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14:53:21

** Use the laws of exponents (mostly x^a / x^b = x^(a-b) as follows:

6^(5/4) / 6^(1/4) =

6^(5/4 - 1/4) =

6^1 =

6. **

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RESPONSE -->

I got it.

self critique assessment: 3

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14:54:48

R.9.36. What steps did you follow to simplify (x^3)^(1/6) and what is your result, assuming that x is positive and expressing your result with only positive exponents?

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RESPONSE -->

Because this is an exponent being raised to an exponent, I multiplied them together to get x^3/6 which equals x^1/2 or the sqrt(x)

confidence assessment: 2

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14:55:06

** Express radicals as exponents and use the laws of exponents.

(x^3)^(1/6) =

x^(3 * 1/6) =

x^(1/2). **

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RESPONSE -->

I got that one.

self critique assessment: 3

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15:06:49

R.9.48. What steps did you follow to simplify (x^(1/2) / y^2) ^ 4 * (y^(1/3) / x^(-2/3) ) ^ 3 and what is your result, assuming that x is positive and expressing your result with only positive exponents?

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RESPONSE -->

(x^1/2) is in simpliest terms

(y^2)^4 = y ^8

(y^1/3) is in simpliest terms

(x^(-2/3))^3= x^-2. I am left with (x^1/2) / (y^8)*(y^1/3)/ x^-2. Then I moved did y^8 * y^1/3 = y^8/3. Then I moved x^-2 beside y^8/3. Then I have (x^1/2) / (y^8/3 x^2). Since I have an exponent divided by an exponent

I subtract them and move the x to the bottom of the fraction, that gives me 1/ (x^3/2 y^8/3)

confidence assessment: 1

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15:08:47

** (x^(1/2) / y^2) ^ 4 * (y^(1/3) / x^(-2/3) ) ^ 3 =

x^(1/2 * 4) / y^(2* 4) * y^(1/3 * 3) / x^(-2/3 * 3)=

x^2 / y^8 * y / x^(-2) =

x^2 * x^2 / y^7 =

x^4 / y^7. **

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RESPONSE -->

I messed up because I didn't realize that (x^1/2 / y^2) was grouped together, I see that now though. I know that x^-2 must be moved to make it positive. I can see that my mistake happened in the first part of the problem.

self critique assessment: 2

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15:10:44

R.9.72. Factor 8 x^(1/3) - 4 x^(-2/3), x <> 0.

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RESPONSE -->

I don't understand the question, how can x be greater than 0 and less that 0 at the same time?

confidence assessment: 0

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15:12:03

** To factor 8x^(1/3)- 4x^(-2/3) we first need to write the expression without negative exponents. To accomplish this we multiply through by x^(2/3) / x^(2/3), obtaining

(8 x^(1/3 + 2/3) - 4x^(-2/3 + 2/3) / x^(2/3) =

(8 x - 4) / x^(2/3). We then factor 2 out of the numerator to obtain

4 ( 2x - 1) / x^(2/3).

Other correct forms include:

( 4x^(1/3) ) ( 2 - ( 1/x) )

8 x^(1/3) - 4 / x^(2/3). **

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RESPONSE -->

The x<>0 must have just been a typo. I understand how to factor this problem by multiplying everything by x^2/3, and how you got the correct answer.

self critique assessment: 2

<> means 'greater or less', which is the same as 'not equal to'. Go by the statement of the problem in your text.

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15:13:02

Add comments on any surprises or insights you experienced as a result of this assignment.

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RESPONSE -->

I realized that exponents can be tricky, and sometimes it is hard for me to decide which law to use to solve a particular problem.

confidence assessment: 3

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These problem can be challenging. You're doing very well with them. Let me know if you have additional questions.