Solve the problem.
-The formula $N = 4 x ^ { 2 } + 5 x + 3$ 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 87 thousand households with computers in this city?
A) 1994
B) 1993
C) 1992
D) 1995

Question

Quizplus · Accepted Answer

To find the year when there were 87 thousand households with computers, we set $N = 87$ and solve for $x$:$$87 = 4x^2 + 5x + 3$$Subtract 87 from both sides to set the equation to 0:$$4x^2 + 5x + 3 - 87 = 0$$$$4x^2 + 5x - 84 = 0$$Factoring or using the quadratic formula, we find that $x = 4$ is a solution that makes sense in this context (years after 1990).Thus, the year is $1990 + 4 = 1994$.

Solve the Problem N=4x2+5x+3N = 4 x ^ { 2 } + 5 x + 3N=4x2+5x+3

Solve the Problem $N = 4 x ^ { 2 } + 5 x + 3$