Regular exercise can help a person lower their resting heart rate. Suppose an individual's resting heart rate, in beats per minute, is modeled by the function(x) = -0.2 -0.6x2 + 85 after x weeks of regular exercise. How many weeks of exercise are necessary to lower the individual's resting heart rate below 70 beats per minute?
(25 points)
A 7 weeks
B. 8 weeks
DC 9 weeks
D. 10 weeks
Question 4 of 4