Find the fourth, sixth, and thirteenth terms of the sequence described by each
explicit formula.
15. a(n) = 6 + (n - )
16. a(n) = 12 + (n - 1)(5)
17. a (n) = -2.2 + (n - )
18. a(n) = 5 + (n - 1)(0.5)
19. a(n) = -3 + (n - 1)6)
20. a(n) = -7.6+ (n 1)(3)

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)

He weights of 2-pound bags of best dog food are approximately normally distributed with a given mean  and standard deviation  according to the empirical rule, what percentage of the bags will have weights within 3 standard deviations of the mean? 47.5%68%95%99.7%

The length of a rectangle plus its width is 24 cm. the area is 143 square cm. what are the length and width of the rectangle?