9. write the equation in standard form: 25x2 –16y2 = 400

Ateacher asked his students to vote for an animal to be their class pet. five-eighteenths of the students voted for a rabbit, voted for a snake, and voted for a hamster. which statement is true? more students voted for a hamster than a snake. more students voted for a snake than a rabbit. more students voted for a rabbit than a hamster. more students voted for a snake than a hamster.

Solve the equation -9p - 17 =10 a -3 b. 16 c. 18 d -16

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) = .