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Math Help - Set y = 0?

  1. #1
    Junior Member
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    Set y = 0?

    The question first tells me to graph the function to determine any x-intercepts.
    y = 20(2/X+1 - 3/x)
    When I put it in my calculator, I got x-intercept = (1,0)
    Now it tells me to set y = 0 to confirm this result.
    So,
    0 = 20(2/X+1 - 3/x)
    I started working in the brackets:
    (2x)/(x)(x + 1) - (3x+1)/(x)(x+1)
    (-x+1) / (x)(x+1)
    Is this right?
    If so, what do I do next? What do I do with the 20?
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  2. #2
    Super Member
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    Israel
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    Quote Originally Posted by tsmith View Post
    The question first tells me to graph the function to determine any x-intercepts.
    y = 20(2/X+1 - 3/x)
    When I put it in my calculator, I got x-intercept = (1,0)
    Now it tells me to set y = 0 to confirm this result.
    So,
    0 = 20(2/X+1 - 3/x)
    I started working in the brackets:
    (2x)/(x)(x + 1) - (3x+1)/(x)(x+1)
    (-x+1) / (x)(x+1)
    Is this right?
    If so, what do I do next? What do I do with the 20?
    \frac{2x}{x(x+1)} - \frac{3x+1}{x(x+1)} \neq \frac{2}{x+1} - \frac{3}{x} = \frac{2x}{x(x+1)} - \frac{3(x+1)}{x(x+1)}  = \frac{2x - 3(x+1)}{x(x+1)} = \frac{-x-3}{x(x+1)}

    Can you solve \frac{-3-x}{x(x+1)} = 0 ?
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  3. #3
    Junior Member
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    Sep 2009
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    -3/(x+1)?
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  4. #4
    -1
    e^(i*pi)'s Avatar
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    West Midlands, England
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    Quote Originally Posted by tsmith View Post
    -3/(x+1)?
    x = -3

    Take tsmith's final working:

    <br />
\frac{-3-x}{x(x+1)} = 0<br />

    Multiply both sides by x(x+1)

    -3-x = 0

    Can you see x = -3 now?
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