Mobile ad spending. The amount spent worldwide in advertising on mobile devices can be estimated by f(x) =0.4x^2+0.01x+0.9. Where x is the number of years after 2005 and f(x) is in billions of dollars. When will worldwide mobile ad spending reaches $41 billion?

solve 41 = .4x^2 + .01x + .9

multiply by 100
40x^2 + x + 90 = 4100
40x^2 + x - 4010 = 0
x = (-1 ± √641601)/80 = 10 or a negative

it will take 10 yrs

To find out when worldwide mobile ad spending reaches $41 billion, we need to solve the equation 0.4x^2 + 0.01x + 0.9 = 41.

To do this, we can rearrange the equation to make it equal to zero:

0.4x^2 + 0.01x + 0.9 - 41 = 0.

Now, we have a quadratic equation in the form ax^2 + bx + c = 0, where a = 0.4, b = 0.01, and c = 0.9 - 41.

The next step is to solve the quadratic equation. There are several methods to solve quadratic equations, such as factoring, completing the square, or using the quadratic formula. In this case, we will use the quadratic formula:

x = (-b ± sqrt(b^2 - 4ac)) / (2a).

Using the values a = 0.4, b = 0.01, and c = -40.1, we can substitute them into the quadratic formula equation:

x = (-0.01 ± sqrt((0.01)^2 - 4 * 0.4 * (-40.1))) / (2 * 0.4).

After performing the calculations, we get two possible values for x: x ≈ -75.04 and x ≈ 125.29.

However, since we are looking for the number of years after 2005, we need to disregard the negative value. Therefore, the worldwide mobile ad spending reaches $41 billion approximately 125.29 years after 2005.

To find the actual year, we add 125.29 to 2005:

Year = 2005 + 125.29 = 2130.29.

Hence, worldwide mobile ad spending will reach $41 billion around the year 2130.