1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Factoring Help, Finding two variables

  1. Sep 15, 2014 #1
    1. The problem statement, all variables and given/known data

    If f(x) = mx^3 + gx^2 - x + 3 is divided by x - 1, the remainder is 3. If f(x) is divided by x + 3, the remainder is -1. What are the values of m and g?

    2. Relevant equations

    Remainder Theorum/Factor Theorum

    3. The attempt at a solution

    Here is what I did:


    x -1 remainder = 3


    x + 3, remainder = -1


    Past that point is where I start getting fractions to my answers which don't lead me anywhere close to my answer. Where did I make a mistake and how can I solve it?
  2. jcsd
  3. Sep 15, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Shouldn't those -7's be -1's? And I think the (small) fractions you get will work.
  4. Sep 16, 2014 #3
    Yeah, I messed up the equation:


    collect like terms:


    -1=(-27/7)n - (-9/7)g

    As you can see I end up with some strange numbers. I never got the correct answer with them so I assume they're wrong. And yet, there's no possible way I can get a -9 or even a -3 to factor those numbers.
    Last edited: Sep 16, 2014
  5. Sep 16, 2014 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    You have ##m+g=1## and ##-27m+9g = -7##. Two equations and two unknowns. Just solve them.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted