Solve the problem.
-The formularmula $N = 3 x ^ { 2 } + 5 x + 2$ represents the number of households, N, in thousands, in a certain city that have a computer x years after 1990. According to the formula, in what year were there 102,000 households with Computers in this city?
A)1996
B)1993
C)1994
D)1995

Question

Quizplus · Accepted Answer

To find the year when there were 102,000 households with computers, set $N = 102$ (since N is in thousands) and solve for x:  $102 = 3x^2 + 5x + 2$.  Rearrange to: $3x^2 + 5x - 100 = 0$.  Using the quadratic formula, $x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$, where $a = 3$, $b = 5$, and $c = -100$, solve for x.  The solution gives $x = 5$.  Since x is the number of years after 1990, the year is 1990 + 5 = 1995.

Solve the Problem N=3x2+5x+2N = 3 x ^ { 2 } + 5 x + 2N=3x2+5x+2

Solve the Problem $N = 3 x ^ { 2 } + 5 x + 2$