Please help me w/ algebra problem! Difference quotients...

Discussion in 'General' started by syntax13, Sep 25, 2007.

  1. Anyone who helps will get +repped. This college algebra quiz is due in an hour and I need to verify one of the problems. Here it is:

    Compute and simplify the difference quotient. [f(x+h)-f(x)] / h.

    f(x) = 6x^2+9x

    My answer was 6h^2 + 9h + 18x.

    If this is right, just let me know, but I'm not too sure it is, so if it isn't please tell me how you got what you did.

    Help a stoner out! I'll positive rep anyone who gives it a shot.
  2. It's been a while since I've done math, but I got 6h + 12x + 9.
  3. Thanks homie, +rep
  4. Yeah Buffet that's the right answer.

    Here's the work:

    I love math.
  5. nice lil problem, startin to get near some calc type stuff..

    heres how i did it:
    (6(x+h)^2 + 9(x+h) - 6x^2 +9x) / h

    expanding (x+h)^2 and multiplying by 6:
    (6x^2 + 12xh + 6h^2 + 9x +9h - (6x^2 +9x)) / h

    (12xh +6h^2 +9x +9h - 9x) / h

    (12xh +6h^2 + 9h) / h

    12x + 6h + 9

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