Math Help Forum - Pre-Algebra and Algebra http://www.mathhelpforum.com/math-help Basic calculations, order of operations, basic matrices, solving for variables, functions, logs and exponents and more en Fri, 20 Nov 2009 21:44:36 GMT vBulletin 60 http://www.mathhelpforum.com/math-help/images/MHF/misc/rss.jpg Math Help Forum - Pre-Algebra and Algebra http://www.mathhelpforum.com/math-help Regression, differences and their formulas http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115767-regression-differences-their-formulas.html Fri, 20 Nov 2009 17:58:38 GMT The question: For this exercise, round all regression parameters to three decimal places. In the fishery sciences it is important to determine the length of a fish as a function of its age. One common approach, the von Bertalanffy model, uses a decreasing exponential function of age to... The question:

For this exercise, round all regression parameters to three decimal places.

In the fishery sciences it is important to determine the length of a fish as a function of its age. One common approach, the von Bertalanffy model, uses a decreasing exponential function of age to describe the growth in length yet to be attained; in other words, the difference between the maximum length and the current length is supposed to decay exponentially with age. The following table shows the length L, in inches, at age t, in years, of the North Sea sole.

t = age L = Length
1 |3.7
2 |7.5
3 |10
4 |11.5
5 |12.7
6 |13.5
7 |14
8 |14.4
Suppose the maximum length attained by the sole is 15.0 inches.

(a) Make a table showing, for each age, the difference D between the maximum length and the actual length L of the sole.

t = age D = Difference
 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |0.6
(I was only able to get row 8 by using the information underneath the previous table.)

(b) Find the exponential function that approximates D. (Round all regression parameters to three decimal places.)

D =

(c) Find a formula expressing the length L of a sole as a function of its age t. (Round all parameters to three decimal places.)

L =
(I thought this would be 4.877(1.176)^t, but that was incorrect.) ]]> Pre-Algebra and Algebra MathBane http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115767-regression-differences-their-formulas.html Make a perfect square http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115742-make-perfect-square.html Fri, 20 Nov 2009 15:08:03 GMT I need to make 8x^2+36x a perfect square, which number would i add to it to do so?(this is for parametric sequences in calc 2, but i just need to know the number i use to make that part a perfect square) I need to make 8x^2+36x a perfect square, which number would i add to it to do so?(this is for parametric sequences in calc 2, but i just need to know the number i use to make that part a perfect square) ]]> Pre-Algebra and Algebra Juggalomike http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115742-make-perfect-square.html Quadratic Problem/Frustrum of a cone http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115732-quadratic-problem-frustrum-cone.html Fri, 20 Nov 2009 12:49:31 GMT Hi Everyone, Can someone have a look at the attachment and let me know where I am going wrong? Thanks....Mark Hi Everyone,

Can someone have a look at the attachment and let me know where I am going wrong?

Thanks....Mark
Attached Thumbnails
Click image for larger version Name: 20-11-2009 12-23-14_0031.jpg Views: N/A Size: 190.2 KB ID: 13931  
]]> Pre-Algebra and Algebra manich44 http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115732-quadratic-problem-frustrum-cone.html Word problem, US dollar and China Yuan http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115726-word-problem-us-dollar-china-yuan.html Fri, 20 Nov 2009 12:12:12 GMT This is not a formal word problem in the sense that I stumbled upon it in a text book, but rather a discussion between myself and a friends parent. The context of the word problem is as follows. Currently the US has a very large deficit with most of the debt being owned by China. The parent... This is not a formal word problem in the sense that I stumbled upon it in a text book, but rather a discussion between myself and a friends parent.

The context of the word problem is as follows. Currently the US has a very large deficit with most of the debt being owned by China. The parent stated if China were to stop deflating its own currency, and raise it so its worth more, the actual debt we owe in China would shrink.

I have thought about this and tried to work it out but Im not sure if im doing something wrong or if my friends mom is incorrect.

(Im not sure how to set this up correctly, nor the proper questions to ask)

As of 10/17/2009
1 Yuan = .1464 $ (usd)
1 USD = 6.8285 ¥ (yuan)

Lets say China owns $50,000 of total US debt.

I fail to see a scenario where USD debt would shrink from a strengthening yuan. ]]> Pre-Algebra and Algebra allyourbass2212 http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115726-word-problem-us-dollar-china-yuan.html Matrix elimination: http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115723-matrix-elimination.html Fri, 20 Nov 2009 11:54:27 GMT Find the values of t for which the system of equations x - y - 2z = -3 tx + y - z = 3t x + 3y + tz = 13 does not have a unique solution for x, y and z. Show that, for one of these values of t, no solution exists and for the other values of t, find the solution set. Find the values of t for which the system of equations
x - y - 2z = -3
tx + y - z = 3t
x + 3y + tz = 13
does not
have a unique solution for x, y and z.
Show that, for one of these values of t, no solution exists and for the other values of t,
find the solution set. ]]> Pre-Algebra and Algebra karldiesen http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115723-matrix-elimination.html Adding a monster of a rational expression http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115690-adding-monster-rational-expression.html Fri, 20 Nov 2009 04:25:04 GMT I am having a hard time with this, I am not sure if its just the sheer size or something in my calculations. I am grateful to anyone who wants to take this on: 4a^2-20a/a^2+2a-35 + 3a-6/3a^2-10a+8 So far all I have is the simplified version of the two denominators (a+7)(a-5) (3a-4)(a-2) ... I am having a hard time with this, I am not sure if its just the sheer size or something in my calculations. I am grateful to anyone who wants to take this on:

4a^2-20a/a^2+2a-35 + 3a-6/3a^2-10a+8

So far all I have is the simplified version of the two denominators
(a+7)(a-5) (3a-4)(a-2)

Then after this the equation is too huge for me to deal, with it seems. ]]> Pre-Algebra and Algebra Charchar http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115690-adding-monster-rational-expression.html Need help factoring http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115684-need-help-factoring.html Fri, 20 Nov 2009 03:58:03 GMT Hi I was wondering if anyone could help me with this equation i have, im trying to factor this in my ti92+ calculator and im not seeing the textbook result my book shows. Im told to factor this 1/9*y^2 - 1/6*y*x^2 + 1/16*x^4 the answer the book gives is (1/3*y - 1/4*x^2)^2 is... Hi
I was wondering if anyone could help me with this equation i have, im trying to factor this in my ti92+ calculator and im not seeing the textbook result my book shows. Im told to factor this

1/9*y^2 - 1/6*y*x^2 + 1/16*x^4

the answer the book gives is

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

is there anything special i need to do to factor this equation.
The calculator gives me this as the answer

(3*x^2 - 8)^2 / 144

I know if i factor it by hand i can get the proper answer but i have alot of these to do and im not sure what im doing wrong. Ive also tried this in the sage math application and it didnt show the proper form either.


Any help would be appreciated thanks. ]]> Pre-Algebra and Algebra newbie43 http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115684-need-help-factoring.html Rearrange formula http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115682-rearrange-formula.html Fri, 20 Nov 2009 03:40:33 GMT i need to make c the subject in this formula? any help would be nice please. s=c+mt i need to make c the subject in this formula? any help would be nice please.

s=c+mt ]]> Pre-Algebra and Algebra nexer http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115682-rearrange-formula.html Gradients http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115678-gradients.html Fri, 20 Nov 2009 03:18:21 GMT Sorry can anyone help me through making a gradient from the points (22,7100) and (20,5800). Please struggling. Sorry can anyone help me through making a gradient from the points (22,7100) and (20,5800). Please struggling. ]]> Pre-Algebra and Algebra nexer http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115678-gradients.html Gaus Jordan ELimination compared to cofactor inverse matrix http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115673-gaus-jordan-elimination-compared-cofactor-inverse-matrix.html Fri, 20 Nov 2009 03:04:37 GMT Hey guys i am stuck with the gaus jordan method of the following matrix. _A_ = 1 2 3 4 5 6 3 1 -2 For the co factor i worked out the C transpose as: 1/3 (-16 7 3 26 -8 6 Hey guys i am stuck with the gaus jordan method of the following matrix.

A = 1 2 3
4 5 6
3 1 -2

For the co factor i worked out the C transpose as:

1/3 (-16 7 3
26 -8 6
-11 5 -3)

The gaus jordan is suppoesed to agree with my final cofactor matrix but i cant seem to understand how to get there?? i have donw the row eliminations to get the diagonal as 1 and the rest as 0.


Add (-4 * row1) to row2

Add (-3 * row1) to row3

Divide row2 by -3

Add (5 * row2) to row3

Divide row3 by -1

Add (-2 * row3) to row2

Add (-3 * row3) to row1

Add (-2 * row2) to row1

But now i don't understand what i have to do now? ]]> Pre-Algebra and Algebra Latkan http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115673-gaus-jordan-elimination-compared-cofactor-inverse-matrix.html Systems of Equations application problem http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115672-systems-equations-application-problem.html Fri, 20 Nov 2009 03:01:21 GMT I'm not sure how to even begin to solve this:
You have boxes of five types. They are characterized by their length , their width , their height , their age , and their price , as given in the following table:

So for example, boxes of type IV measure 1 by 2 by 4 feet, are a year old, and cost $ 2.- each. Suppose the sum of the lengths of your boxes is 30, the sum of their widths 49, the sum of their heights 87, the sum of their ages 40, and the total price of those boxes 55.
You have

boxes of type I_____
boxes of type II_____
boxes of type III_____
boxes of type IV_____
boxes of type V______

Do the numbers corresponding to the length, height, width, sum and price go on the right hand side of the system, and then just solve?

e.g.1 1 1 1 1 = 30
1 1 2 3 2 = 49
1 2 3 2 2 = 87
1 2 4 1 2 = 40
1 2 3 1 3 = 55 ]]> Pre-Algebra and Algebra thebristolsound http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115672-systems-equations-application-problem.html Elimination http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115666-elimination.html Fri, 20 Nov 2009 02:17:17 GMT ok so i have a solving problem about substitution
Taxis in a certain city charge a flat fee plus an additional charge per kilometer. Russ was charge $3.20 for a 5-km ride and Kylie was charged $4.20 for a 9-km ride. Someone lay out the 2 equations since i can't seem to figure out the two equations? (Worried) ]]> Pre-Algebra and Algebra katt http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115666-elimination.html Question about Probability - Arrange set of Numbers http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115643-question-about-probability-arrange-set-numbers.html Fri, 20 Nov 2009 00:07:47 GMT Dear all, I was given a set of number "0000011" and asked how many different arrangement I can make with only this set of number.

I tried to list all possible arrangements (0100001, 0001001.......) But it takes way too long. I am think of using the formula of Permutation, am i on the right track?

Thanks! ]]> Pre-Algebra and Algebra mak15 http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115643-question-about-probability-arrange-set-numbers.html 2 by 2 gaussian elimination help...wtf is this q asking? http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115642-2-2-gaussian-elimination-help-wtf-q-asking.html Fri, 20 Nov 2009 00:07:40 GMT Is this a possible gaussian elimination. It is asked in a genuine question for gaussian elimination btw. 2x + 3y = 5 6x + 9y = 15 As a matrix it looks like 2 3 |5 6 9 |15 Is this a possible gaussian elimination. It is asked in a genuine question for gaussian elimination btw.

2x + 3y = 5
6x + 9y = 15

As a matrix it looks like

2 3 |5
6 9 |15

But when you do: row 2- 3*row 1
you get 0 0 0 in the bottom row and now way of working out the x & y values......am i missing something here? ]]> Pre-Algebra and Algebra Latkan http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115642-2-2-gaussian-elimination-help-wtf-q-asking.html Exponential Equation help! http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115633-exponential-equation-help.html Thu, 19 Nov 2009 22:38:04 GMT How would I go about doing problems such as e^x+1=1/e and e^x+4=1/e^2x Thanks! How would I go about doing problems such as

e^x+1=1/e

and

e^x+4=1/e^2x

Thanks! ]]> Pre-Algebra and Algebra The Masked Trumpet http://www.mathhelpforum.com/math-help/pre-algebra-algebra/115633-exponential-equation-help.html