1: Add or Subtract: (-2x^2 - 4x + 8) + (5x^2 + 2x - 25)
2: Add or Subtract: (5x^2 + 4x - 6) - (-5x^2 - 3x + 15)
3: Multiply: (3x - 1)(4x^2 + 3x + 7)
4: Find the roots: f(n) = n^2 - 2n - 15

Show your work please and thank you! Need answers ASAP

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.