High concentrations of carbon monoxide CO can cause coma and possible death. The time required for a person to reach a COHb level capable of causing a coma can be approximated by the quadratic model
T=.0002x^2 - .316x + 127.9 where T is the exposure time in hours necessary to reach this level and 500 ≤ x ≤ 800 is the amount of carbon monoxide present in the air in parts per million (ppm).
a) What is the exposure time when x= 800?
b) Estimate the concentration of CO necessary to produce a coma in
(a) just substitute x=800 into the equation for T
(b) set T=9 and solve the quadratic to find possible values for x. If any value lies outside the range 500...800 then discard it for this exercise.
You have memorised a general formula for solving a quadratic, use it here. 😃
Here's a refresher: http://www.purplemath.com/modules/quadform.htm