(Iv'e posted this question before, but I forgot the multiple choice answers)
Which is the simplified version of 7x−4(x−8)=56?

A: 11x+32=56
B: 3x−8=56
C: 3x-32=56
D: 3x+32=56

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) = .