Help me plzz and thanks

Which of the expressions (on the photo document i inserted) together represent all solutions to the following equation? 8cos(12x)+4=-4 *the answer should be in degrees.* > i would like for someone to explain the process to find the solutions for this.

On #16 : explain how factoring a trinomial, ax^2+ bx+ c, when a does not equal 1 different from factoring a trinomial when a = 1.

Arectangle has a length of 6cm by 8cm what is the length of a diagonal of the rectangle