Algebraic equation

Question

Use of the internet in a country is given by the function (x)= 0.485x^2-1.694x+0.315, where the output is in millions of users, so this formula=6 corresponds to 1996, x=7 corresponds to 1997, and on until x+20 corresponds to 2010, so estimate when the number of internet users in the country reached 127 million.

Answer 1

f(x)=0.485x²-1.694x+0.315.

Given: f(6) is the millions of users in 1996 and f(7) is that in 1997, we can deduce that x=year-1990.

When f(x)=127:

0.485x²-1.694x+0.315=127,

0.485x²-1.694x-126.685=0.

Use quadratic formula to solve:

x=(1.694±√(1.694²+√245.7689)/0.97,

x=18 approx. (We reject the negative solution because we are predicting a future (positive) value.)

So in 1990+18=year 2008, the estimated number of users reaches 127 million.

As an addendum, the 1996 number was about 7.61 million and that for 1997 was about 12.22 million users.