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Mathematics 7 Online
eviant:

Math help

eviant:

1 attachment
eviant:

@Zepdrix

Zepdrix:

Let's use the year 2000 as our starting point to model our exponential function.

Zepdrix:

So year 2000 is like year 0 for our function. When x=0, the population=571044

Zepdrix:

\[\large\rm f(x)=a\cdot b^x\]\[\large\rm f(0)=571044=a\cdot b^0\]\[\large\rm 571044=a\] So that gives us part of the information we need, our starting coefficient for the exponential.

Zepdrix:

Errr wait wait wait, is that what they want us to do? :d sec thinking

Zepdrix:

Ya ya ya, then we'll use another data point to find an appopriate base value for our exponential.

Zepdrix:

\[\large\rm f(x)=571044\cdot b^x\] In 2005, think of this as 5 years after our starting point, x=5, and population=550521\[\large\rm f(5)=550521=571044\cdot b^5\]

Zepdrix:

Let's divide our exponential's coefficient to the other side,\[\large\rm \frac{550521}{571044}=b^5\]

Zepdrix:

To undo a 5th power, we'll take a 5th root.\[\large\rm \sqrt[5]{\frac{550521}{571044}}=\sqrt[5]{b^5}\]

Zepdrix:

Using a calculator gives us a value of abouttttttt ... 0.992706595

Zepdrix:

So \(\rm b\approx 0.993\)

Zepdrix:

\[\large\rm f(x)=571044(0.993)^x\]

eviant:

a ∙ bx = (550,521)(0.992)x a ∙ bx = (550,521)(0.990)x a ∙ bx = (550,521)(0.991)x a ∙ bx = (550,521)(0.993)x

Zepdrix:

Something like that. Assuming I didn't mess up a number somewhere along the way x'D

Zepdrix:

Oh you have options, nice

Zepdrix:

Oh they used 2005 as the starting point, ok that's weird x'D

Zepdrix:

Wish you had given the options before all that math .... -_-

eviant:

sorry

eviant:

I didn't realize you'd need the options for this

Zepdrix:

Sec thinking :d They're using 2005 as the starting point, so all the other values would be negative in relation... hmm seems weird

Zepdrix:

Using the new numbers I'm coming up with, b=0.992706495 maybe that's the same value as before <.< i dunno lol f(x) = 550521 * (0.993)^x

Zepdrix:

Ya ya I think the last option is the one we want :O

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