The Math Forum

Ask Dr. Math - Questions and Answers from our Archives
Associated Topics || Dr. Math Home || Search Dr. Math

Polynomials with x

Date: 9/10/96 at 17:2:23
From: Joe
Subject: Polynomials With x

Can you help me figure out problems like
 3x-x(3-5x)=(5x-2)(x+4)  ?


Date: 9/12/96 at 12:34:43
From: Doctor Leigh
Subject: Re: Polynomials With x

Thank you for your question!!!

    3x-x(3-5x)=(5x-2)(x+4)       First distribute
    3x-3x+5x^2 = 5x^2-2x+20x-8   Then combine like terms
    5x^2 = 5x^2+18x-8            Move all the x's to one side
    -5x^2  -5x^2
    0 = 18x-8                    Add 8 to both sides
    8 = 18x                      Divide by 18

    8/18 = x

The steps for problems like this are:

1. follow your order of operations - do each operation indicated
   (multiplication, etc.)
2. combine like terms
3. get all of the x's over to one side
4. solve for x

You try the rest!

-Doctor Leigh Ann,  The Math Forum
 Check out our web site!   
Associated Topics:
Middle School Algebra

Search the Dr. Math Library:

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.