Mr. nevin buys a car for $18,500. the value of the car depreciates 9% per year; 7 year

Apackage of bacon holds 15 strips of bacon. the pancake house uses 17 packages of bacon in the morning and 21 packages in the afternoon. how many more strips were used in the afternoon than the morning?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).