D= {xlx is a whole number}
e = {xlx is a perfect square between 1 and 9}
f = {xix is an even number greater than or equal to 2 and less than 9}
which of the following is dn f?
a. (4,6)
b. {2,4,61
c. {2,4,6,8)
d. {2}

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

1jessica's home town is a mid-sized city experiencing a decline in population. the following graph models the estimated population if the decline continues at the same rate. select the most appropriate unit for the measure of time that the graph represents. a. years b. hours c. days d. weeks

Prove (a) cosh2(x) − sinh2(x) = 1 and (b) 1 − tanh 2(x) = sech 2(x). solution (a) cosh2(x) − sinh2(x) = ex + e−x 2 2 − 2 = e2x + 2 + e−2x 4 − = 4 = . (b) we start with the identity proved in part (a): cosh2(x) − sinh2(x) = 1. if we divide both sides by cosh2(x), we get 1 − sinh2(x) cosh2(x) = 1 or 1 − tanh 2(x) = .