SOLUTION: Suppose that N= cube-root (x) + 2x + 2 models the number of cases of an infection, in millions, of a disease x years from now. a) Approximately how many cases of the infection

Algebra ->  Square-cubic-other-roots -> SOLUTION: Suppose that N= cube-root (x) + 2x + 2 models the number of cases of an infection, in millions, of a disease x years from now. a) Approximately how many cases of the infection       Log On


   

Question 196742: Suppose that N= cube-root (x) + 2x + 2 models the number of cases of an infection, in millions, of a disease x years from now.
a) Approximately how many cases of the infection will there be 16 years from now?
b) In approximately how many years will there be 7 million cases?
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
a) N=++x%5E%281%2F3%29+%2B+2x+%2B+2
N+=+16%5E%281%2F3%29+%2B+16%2A2+%2B+2
N+=+2.52+%2B+32+%2B+2
N+=+36.52million
b) You could solve this algebraically and the plot it OR you could think a little and find the answer emperically (trial and error). In this case, trial and error is quicker.
Try 1. Then N = 1+2+2 = 5 (not quite 7)
Try 2. Then N = 1.25+4+2 = 7.25
So the answer is 'a little less than 2 years'.
Try 1.9. Then N = 1.23 + 3.8 + 2 = 7.03
Close enough for me. 1.9 years works :)