The radius of a circle is 4 miles. what is the circles circumference

Solve the system of equations. y= 2x y= x^2 - 15

If a || b and b | y, then ? a) x || y. b) x | a. c) a | y. d) a || y.

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.