Select the correct answer. Plutonium–238 has a yearly decay constant of 7.9 × 10-3. If an original sample has a mass of 15 grams, how long will it take to decay to 12 grams?

(At = A0e-kt)

A.
3 years

B.
12.3 years

C.
28.3 years

D.
139.1 years

Which compound inequality could be represented by the graph?

At a kentucky friend chicken, a survey showed 2/3 of all people preferred skinless chicken over the regular chicken. if 2,400 people responded to the survey, how many people preferred regular chicken?

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) = .