1. Not finding help here? Sign up for a free 30min 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!

Grade 9/10 Algebra.

  1. Sep 9, 2009 #1
    (8y squared + 5y -7) - ( 9y squared + 3x -3)

    This is my friends, and i'm trying to hlep him on it.
    And the answer in the book is -y squared +8y -12
    and we can't figure out how to get it.
     
  2. jcsd
  3. Sep 9, 2009 #2

    Astronuc

    User Avatar

    Staff: Mentor

    Well something is missing in the initial equation.

    (8y2 + 5y -7) - (9y2 + 3x -3) = 0 ?

    and one is solving for x?

    or (8y2 + 5y -7) - (9y2 + 3y -3) = ?

    in which case one simply groups the corresponding monomials, or powers of y.


    This looks like homework so I'll move it to the precalculus HW forum.
     
  4. Sep 9, 2009 #3
    I don't think that's what it's asking for. It's just simplifying it.
    I wrote what it says the answer is.
    But i got like -y squared -3x+5y-4
     
  5. Sep 9, 2009 #4
    If all you are supposed to do is simplify the expression, and that line is all that you are given about x and y, then the book is incorrect.
     
  6. Sep 9, 2009 #5
    okay, i thought the book was wrong but just thought i'd make sure.
    and there is no way 7 and 3 can make 12.
     
  7. Sep 9, 2009 #6
    One of three things could be happening:

    (1) There is a typo in the book (it happens) and the problem should have read

    [tex](8y^2+5y+7)-(9y^2-3y-5)[/tex].

    (2) The person who wrote the solution erred (it happens - solution manual writers are rarely the original text authors).

    (3) There is somewhere an assumption that [itex]x = \frac{22}{3}-y[/itex].

    Regardless, the problem as stated and the given answer do not correspond.

    --Elucidus
     
  8. Sep 10, 2009 #7

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    [itex](8y^2+ 5y- 7)[/itex][itex]- (9y^2+ 3x- 3)[/itex][itex]= (8y^2- 9y^2)+ (5y- 3y)+ (-7- (-3))[/itex] is NOT [itex]-y^2+ 8y- 12[/itex].
     
  9. Sep 10, 2009 #8
    Especially since there is a 3x in there.

    --Elucidus
     
  10. Sep 10, 2009 #9
    If Jenninifer typed the way he/she should of at his/her first post in this topic, then the answer in the book is wrong!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Grade 9/10 Algebra.
  1. Grade 10, angle problem. (Replies: 15)

  2. MAA Problem 9/22/10 (Replies: 0)

Loading...