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applying differential equations to real-life problems watch

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    (Original post by Alen.m)
    So basically it's a graph of y=30000-20000e^0.2tIn(0.9)? The reason im asking is because the text book stated it's a graph of e^0.2In(0.9t) which should definetely be different Attachment 511585511587
    It's sloppy notation on their part, what they mean is e^{0.2 \ln (0.9) t}
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    (Original post by Zacken)
    It's sloppy notation on their part, what they mean is e^{0.2 \ln (0.9) t}
    how about if i wanna sketch the graph of y=30000-20000e^0.2In(0.9t), in this case actually as t increases the value of e^0.2In(0.9t) increases as well therefore the value of c will decrease and the graph would look like something like this?
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    (Original post by Alen.m)
    how about if i wanna sketch the graph of y=30000-20000e^0.2In(0.9t), in this case actually as t increases the value of e^0.2In(0.9t) increases as well therefore the value of c will decrease and the graph would look like something like this?
    Not quite, if you wanted to sketch that graph, as soon as t > 1.12, the value for the exponential becomes positive, which makes 20 000 e^{\text{blah}} >> 30,000 so your whole thing becomes negative. It would look like this:

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    (Original post by Zacken)
    Not quite, if you wanted to sketch that graph, as soon as t > 1.12, the value for the exponential becomes positive, which makes 20 000 e^{\text{blah}} >> 30,000 so your whole thing becomes negative. It would look like this:

    thanks
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    (Original post by Zacken)
    Not quite, if you wanted to sketch that graph, as soon as t > 1.12, the value for the exponential becomes positive, which makes 20 000 e^{\text{blah}} >> 30,000 so your whole thing becomes negative. It would look like this:

    how about before 1.12 tho? the value of c getting smaller and smaller until t reaches 1.12 then it gets negative ?
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    (Original post by Alen.m)
    how about before 1.12 tho? the value of c getting smaller and smaller until t reaches 1.12 then it gets negative ?
    Yep.
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    (Original post by Zacken)
    Yep.
    Shouldnt it be something like this tho? Coz c start getting negative as t reaches 1.12 but on yours c is already negative before 1.12 Name:  image.jpg
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    (Original post by Alen.m)
    Shouldnt it be something like this tho? Coz c start getting negative as t reaches 1.12 but on yours c is already negative before 1.12 Name:  image.jpg
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Size:  295.4 KB
    That's correct. Look at the scale of my graph. :-)
 
 
 
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