Can someone help me with this

Sketch one cycle if the cosine function y=2cos2theta

What are the solutions of the system? solve by graphing. y = -x^2 -6x - 7 y = 2

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?