testing header
Math Goodies is a free math help portal for students, teachers, and parents.
Free Math
Newsletter
 
 
Interactive Math Goodies Software

Buy Math Goodies Software
testing left nav
Math Forums @ Math Goodies
Math Forums @ Math Goodies
Home | Profile | Register | Active Topics | Members | Search | FAQ
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Homework Help Forums
 Algebra
 Solving Polynomial Equations
 New Topic  Topic Locked
 Printer Friendly
Author Previous Topic Topic Next Topic  

AnnieD
New Member

Canada
2 Posts

Posted - 09/13/2007 :  18:37:10  Show Profile
I have a math assignment due tomorrow and there are a few questions that I don't even know where to begin, how to do, etc. Just overall stumpers. A group of 8 people from the class have been involved in an msn convo for the last 2hr trying to figure them out.. with no luck whatsoever. Any help/tips/start offs, etc. would be very much appreciated!


1) (3x-5)(3x+1) (3x+7) + 68 = 0

Answer: -1 √ 34 , -1 √ 2
*both these answers are over 3




2) (x+6x+6)(x+6x+8) = 528

Answer: -8, 2, - 3 i√ 21




3) The height, length, and width of a small box are consecutive integers with the height being the smallest of the three dimensions. If the length and width are increased by 1cm each and the height is doubled, then the volume is increased by 120cm. Find the dimensions of the original box.

Answer: 3cm, 4cm, 5cm
Go to Top of Page

Subhotosh Khan
Advanced Member

USA
9117 Posts

Posted - 09/13/2007 :  20:23:12  Show Profile
quote:
Originally posted by AnnieD

I have a math assignment due tomorrow and there are a few questions that I don't even know where to begin, how to do, etc. Just overall stumpers. A group of 8 people from the class have been involved in an msn convo for the last 2hr trying to figure them out.. with no luck whatsoever. Any help/tips/start offs, etc. would be very much appreciated!


1) (3x-5)(3x+1) (3x+7) + 68 = 0

Answer: -1 √ 34 , -1 √ 2
*both these answers are over 3




2) (x+6x+6)(x+6x+8) = 528

Answer: -8, 2, - 3 i√ 21




3) The height, length, and width of a small box are consecutive integers with the height being the smallest of the three dimensions. If the length and width are increased by 1cm each and the height is doubled, then the volume is increased by 120cm. Find the dimensions of the original box.

Answer: 3cm, 4cm, 5cm




We do not know where to start - unless you show some work/thoughts.

What have you been taught about solving polynomials, finding roots of polynomial, etc.?

Do you know calculus - do you know numerical analysis?
Go to Top of Page

skeeter
Advanced Member

USA
5634 Posts

Posted - 09/13/2007 :  20:51:44  Show Profile
1. use a substitution ...

let u = 3x+1

[(3x+1)-6](3x+1)[(3x+1)+6] + 68 = 0

(u-6)(u)(u+6) + 68 = 0

u(u-36) + 68 = 0

u4 - 36u + 68 = 0

(u-2)(u-34) = 0

u = 2, u = 34

(3x+1) = 2 , (3x+1) = 34

take it from here?

2. same technique ... let u = x+6x+6

u(u+2) = 528

u + 2u - 528 = 0

(u - 22)(u + 24) = 0

u = 22, u = -24

x+6x+6 = 22, x+6x+6 = -24

finish up.

3. three consecutive ... h, h+1, h+2

V = h(h+1)(h+2)

V + 120 = 2h(h+2)(h+3)

2h(h+2)(h+3) - h(h+1)(h+2) = 120

h(h+2)[2(h+3) - (h+1)] = 120

h(h+2)(h+5) = 120

you should be able to finish from here.
Go to Top of Page

skeeter
Advanced Member

USA
5634 Posts

Posted - 09/14/2007 :  13:16:58  Show Profile
your opinion is noted.
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Topic Locked
 Printer Friendly
Jump To:
Math Forums @ Math Goodies © 2000-2004 Snitz Communications Go To Top Of Page
This page was generated in 0.2 seconds. Snitz Forums 2000
testing footer
About Us | Contact Us | Advertise with Us | Facebook | Blog | Recommend This Page




Copyright © 1998-2014 Mrs. Glosser's Math Goodies. All Rights Reserved.

A Hotchalk/Glam Partner Site - Last Modified 21 May 2014