Factor cot^2x-cotx-42

If x = -2, then x 2-7x+10 equals a. 0 b.20 c.28

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

What are the solutions of the equation x4 – 5x2 – 14 = 0? use factoring to solve. someone !