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Few questions different topics

  1. May 12, 2013 #1
    1. The problem statement, all variables and given/known data

    Find the constants p,q and r such that
    2y2 - 9y+14 = p(y-1)(y-2)+q(y-1) +r

    2) Deduce that (y+1)4 - y^4 < 4(y+1)^3





    The attempt at a solution

    Well I expanded the right side

    and just tried comparing the two equations..

    so I got p =2 ,r =10, q=-3

    is this the correct way of doing this?

    2) (y+1)4 - y^4 - 4(y+1)^3<0

    I did this first, now I don't know where to carry it.
     
  2. jcsd
  3. May 13, 2013 #2

    Office_Shredder

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    p and q are correct but r is wrong.

    Are you really supposed to use these values for p q and r to deduce the second part? Because I don't see the connection at all
     
  4. May 13, 2013 #3
    NO the 2nd part of the question is a totally different question ,sorry. is r 14?
     
  5. May 13, 2013 #4

    Office_Shredder

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    No it's not 14 either. Why don't you write out how you solved for r and we can pinpoint the mistake being made.

    For the second part once you've gotten to that point I recommend expanding everything and canceling a lot of large powers of y
     
  6. May 13, 2013 #5
    I expanded the expression and got py^2 - 3py -12p + qy -q +r

    so I just compared it to the equation stated and said p is =2 because there's also a two on the y^2 in the first equation. Then I said since p = 2 the -3py is now -6y and in the equation there was a -9y so q needs to be -3 to get a -3y. the r ,-12p and the -q need to add up to the 14 so is r 35?
     
    Last edited: May 13, 2013
  7. May 13, 2013 #6

    Office_Shredder

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    That should be a +2p not a -12p
     
  8. May 13, 2013 #7
    ohh I see it, so r should be 15?!!
     
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