In 2009 the average price of a laptop was 803 and the averag

In 2009, the average price of a laptop was $803 and the average price of a desktop PC was $693. The average price of a laptop has decreased by about $143 per year and the average price of a PC has decrease by about $78 per year (Source: Gartner). Let L(t) and D(t) be the average prices (in dollars) of laptops and desktop PCs, respectively, both at t years since 2009. Find equations of L and D. Use the models to predict in what years the average price of a laptop will be less than the average price of a desktop PC.

Solution

a) L(t) = 803 - 143t

D(t) = 693 - 78t

b) We have to find year in which:

L(t) < D(t)

803 - 143t < 693 - 78t

110 < 65t

t > 1.69

So, from 2009 + 1.69 = 2011 onwards the price of laptop will be less than Pc\'s price