The amount spent worldwide in advertising on mobile devices can be estimated by f(x) = 0.4x2 + 0.01x + 0.9, where x is the number of years after 2005 and f(x) is in billions of dollars.
b)When will worldwide mobile ad spending reach $41 billion?
F(x) = Y = 0.4x^2 + 0.01x + 0.9 = 41 B.
Y = 0.4x^2 + 0.01x + 0.9 -41 = 0,
Y = 0.4x^2 + 0.01x - 40.1 = 0,
Use Quadratic Formula to find.
X = 10 Years after 2005 = 2015.