Assignment 13

course Mth 158

ٰϴӟݫassignment #013

013. `query 13

College Algebra

06-29-2008

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19:21:59

**** query 1.5.34 (was 1.5.24). How did you write the interval [0, 1) using an inequality with x? Describe your illustration using the number line.

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RESPONSE -->

0 is less than or equal to x is less than 1

The number line has an closed interval symbol on the number 0 and an open interval symbol on the number 1

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19:24:42

** My notes here show the half-closed interval [0, 1).

When sketching the graph you would use a filled dot at x = 0 and an unfilled dot at x = 1, and you would fill in the line from x = 0 to x = 1. **

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RESPONSE -->

so when graphing use filled and unfilled dots.

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19:25:20

**** query 1.5.40 (was 1.5.30). How did you fill in the blank for 'if x < -4 then x + 4 ____ 0'?

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RESPONSE -->

> is greater than

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19:25:42

** if x<-4 then x cannot be -4 and x+4 < 0.

Algebraically, adding 4 to both sides of x < -4 gives us x + 4 < 0. **

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RESPONSE -->

ok

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19:30:25

**** query 1.5.46 (was 1.5.36). How did you fill in the blank for 'if x > -2 then -4x ____ 8'?

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RESPONSE -->

< less than

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19:32:11

**** query 1.5.58 (was 1.5.48). Explain how you solved the inquality 2x + 5 >= 1.

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RESPONSE -->

Yes I see that the< or > sign has to reversed.

Enter, as appropriate, an answer to the question, a critique of your answer in response to a given answer, your insights regarding the situation at this point, notes to yourself, or just an OK.

Always critique your solutions by describing any insights you had or errors you makde, and by explaining how you can make use of the insight or how you now know how to avoid certain errors. Also pose for the instructor any question or questions that you have related to the problem or series of problems.

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19:33:35

** Starting with

2x+5>= 1 we add -5 to both sides to get

2x>= -4, the divide both sides by 2 to get the solution

x >= -2. **

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RESPONSE -->

I didn't get the question but in solving the inequality add 5 to each side and then divide by 2 to get the solution. x > or = to -2

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19:37:37

**** query 1.5.64 (was 1.5.54). Explain how you solved the inquality 8 - 4(2-x) <= 2x.

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RESPONSE -->

8- 4(2-x) < = -2x

8-8-4x < = -2x

-4x> = -2x

2x > = x

you should have changed the inequality at this point, when you divided both sides by -2.

x > = 0

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19:38:23

** 8- 4(2-x)<= 2x. Using the distributive law:

8-8+4x<= 2x. Simplifying:

4x<=2x. Subtracting 2x from both sides:

2x<= 0

x<=0 **

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RESPONSE -->

I switched my equality sign because I had negatives on both sides.

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19:55:48

** If x = owner cost then

70 < x < 300.

.40 * owner cost is then in the range

.40 * 70 < .40 x < .40 * 300 and $25 + 40% of owner cost is in the range

25 + .40 * 70 < 25 + .40 x < 25 + .40 * 300 or

25 + 28 < 25 + .40 x < 25 + 120 or

53 < 25 + .40 x < 145. **

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RESPONSE -->

I had not typed in my answer before I got the reminder to enter an answer.

Enter, as appropriate, an answer to the question, a critique of your answer in response to a given answer, your insights regarding the situation at this point, notes to yourself, or just an OK.

Always critique your solutions by describing any insights you had or errors you makde, and by explaining how you can make use of the insight or how you now know how to avoid certain errors. Also pose for the instructor any question or questions that you have related to the problem or series of problems.

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19:57:39

**** query 1.5.123 \ 112. Why does the inequality x^2 + 1 < -5 have no solution?

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RESPONSE -->

The x^2 + 1 can never be less than -5.

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19:58:58

STUDENT SOLUTION: x^2 +1 < -5

x^2 < -4

x < sqrt -4

can't take the sqrt of a negative number

INSTRUCTOR COMMENT: Good.

Alternative: As soon as you got to the step x^2 < -4 you could have stated that there is no such x, since a square can't be negative. **

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RESPONSE -->

A square can't be negative could have been a better response.

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Good responses. See my notes and let me know if you have questions. &#