The number of blogs (or weblogs) grew rapidly for several years. According to one report, there were about 2 million blogs in March 2004, after which the number of blogs doubled approximately every six months. Note: Growth tapered off after 2007, and at the end of 2011 there were about 175 million blogs. Let N denote the number (in millions) of blogs and d the number of doubling periods after March 2004. Use a formula to express N as an exponential function of d.

Respuesta :

Answer:

[tex]N(d)=2e^{0.32d}[/tex]

Step-by-step explanation:

Because the growth rate is not constant (as it changes after 2007), then we must find an average rate to use the continue exponential growth function which is given by:

[tex]N(d)=N_{0}e^{rd}[/tex]

Where,

d: number of periods

N(d): total number of blogs in d periods (in millions).

[tex]N_{0}:[/tex]: total number of blogs on the initial period (in millions)

r: average growth rate (this is the one we must find)

With the given information we may consider that:

d=14  The reason for this is that between March 2004 to March 2011 there are 7 years with 14 periods of 6 months(2x7).

N=175 (millions)

[tex]N_{0}=2[/tex] (millions)

Therefore,

[tex]175=2e^{14r}[/tex]

We find r by solving the equation above:

[tex]\frac{175}{2}=e^{14r}[/tex]

[tex]Ln\frac{175}{2}=14r[/tex]

[tex]r=\frac{Ln(175/2)}{14}=0.32[/tex]

Therefore our formula is as it follows:

[tex]N(d)=2e^{0.32d}[/tex]

This is about Exponential decay functions.

N(t) = N₀[tex]e^{0.3194d}[/tex]

  • The general formula to express exponential growth functions is given by;

N(t) = N₀[tex]e^{dr}[/tex]

Where;

N is the amount of blogs remaining after t years

N₀ is the initial amount of blogs

r is the growth rate

d is the number of doubling periods

  • We are given;

N₀ = 2 million blogs

number of years is; 2011 - 2004 = 7 years.

Thus doubling periods is; d = 2 × 7 = 14

N(14) = 175 million

  • Plugging in the relevant values, we have;

175 = 2[tex]e^{14r}[/tex]

divide both sides by 2 to get;

87.5 = [tex]e^{14r}[/tex]

In 87.5 = 14r

14r = 4.4716

r = 4.4716/14

r = 0.3194

Thus;

formula is; N(t) = N₀[tex]e^{0.3194d}[/tex]

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