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alexrobin13

  • one year ago

Find the equation of the function. (please explain so I understand)

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  1. alexrobin13
    • one year ago
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    |dw:1442524295814:dw|

  2. anonymous
    • one year ago
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    Hmm. A tricky one. I think I can help you, if you help me help you :) Based on whatever you've been doing at school, can you make a guess about what sort of function we might need to use? I can think of lots of examples, like sqrt(), tan(), 1/x, and so on. Any guesses?

  3. anonymous
    • one year ago
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    Maybe even exponentials, like exp(-x) or something?

  4. alexrobin13
    • one year ago
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    I'm thinking ln or log function, not sure though

  5. anonymous
    • one year ago
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    Okay, that's certainly sounds possible. Just to check though, is y=4 an asymptote? (i.e. the line gets closer and closer to 4 but doesn't touch it?)

  6. alexrobin13
    • one year ago
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    that's what the graph I have looks like, so I'd say so

  7. ZeHanz
    • one year ago
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    It looks like a rational function: \(y=\dfrac{ax+b}{cx+d}\). If it is, you can find out the values of a, b, c and d by examining the graph: begin with the horizontal asymptote. Because that is y=4, this means a/c=4, so take a=4 and c=1. All you need to do now is substituting (0,0) and (1,2) to find the values of b and d...

  8. ZeHanz
    • one year ago
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    With logarithms you wouldn't get a horizontal asymptote...

  9. ZeHanz
    • one year ago
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    After substituting (0, 0) and (1, 2), I got this:

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  10. ZeHanz
    • one year ago
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    First, try (0, 0): \(0=\dfrac{0+b}{0+d}\), so \(\dfrac{b}{d}=0\), which means c=0.

  11. ZeHanz
    • one year ago
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    Now try (1, 2): \(2=\dfrac{4 \cdot 1}{1+d}\), so \(1+d=\dfrac{4}{2}=2\), which means: \(d=1\). All in all we have: \(y=\dfrac{4x}{x+1}\). There could be othewr formulas, involving the exponential function.

  12. ZeHanz
    • one year ago
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    Like \(y=4-a\cdot e^{-bx}\). Again, the values of a and b can be found by substituting (0, 0) and (1, 2).

  13. alexrobin13
    • one year ago
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    thank you!! that actually helped a lot :)

  14. ZeHanz
    • one year ago
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    YW! When I try the exponential function, I get (after substituting the points (0, 0) and (1, 2)): \(y=4-4e^{-x \ln 2}\) See image. It matches the specs, maybe even better, because the graph rises faster to the asymptote y=4. Looks more like your drawing imo.

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