# Find the Year(s)

• Jan 24th 2010, 05:13 AM
sologuitar
Find the Year(s)
The number N of aids cases diagnosed to date (in thousands) is approximated by the equation
N = -0.37x^2 + 59.5x + 247.26, where x is the number of years since 1990. Assuming that this equation remains valid through the year 2011, determine when the number of diagnosed cases of aids was or will be 1.2 million.

I understand that in the question, N = 1.2 million. I then used the quadratic formula to find x. However, when I replaced N with 1.2, I got the wrong year and thus the wrong answer. What should N be to get the right answer?
• Jan 24th 2010, 07:29 AM
skeeter
Quote:

Originally Posted by sologuitar
The number N of aids cases diagnosed to date (in thousands) is approximated by the equation
N = -0.37x^2 + 59.5x + 247.26, where x is the number of years since 1990. Assuming that this equation remains valid through the year 2011, determine when the number of diagnosed cases of aids was or will be 1.2 million.

I understand that in the question, N = 1.2 million. I then used the quadratic formula to find x. However, when I replaced N with 1.2, I got the wrong year and thus the wrong answer. What should N be to get the right answer?

N is in thousands ... 1.2 million = 1200 thousand
• Jan 24th 2010, 08:57 PM
sologuitar
N = 1200
Quote:

Originally Posted by skeeter
N is in thousands ... 1.2 million = 1200 thousand

1.2 times 1000 = 1200 and then I let N = 1200.

I got the right year this time. Thanks!