Question 821958: The formula N = 4x2 + 5x + 1 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 175 thousand households with computers in this city?
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! ---
N(x) = 4x^2 + 5x + 1
N(x) = 175 = 4x^2 + 5x + 1
4x^2 + 5x - 174 = 0
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the above quadratic equation is in standard form, with a=4, b=5, and c=-174
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
4 5 -174
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the two real roots (i.e. the two x-intercepts), of the quadratic are:
x = 6
x = -7.25
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the negative root doesn't make sense for this problem, so use the positive root
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answer:
in the year = 1990 + x = 1996
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