Find the exact value of cos(-7pi/4 radian).

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

(c) the diagram shows the first three shapes of a matchsticks arrangement. first shape = 3second shape = 5third shape = 7given m represents the number of matchstick used to arrange the n'th shape.(i) write a formula to represent the relation between m and n. express m as the subjectof the formula.(ii) 19 matchsticks are used to make the p'th shape. find the value of p.

X/y + 4y/x divided by x/y - 2y/x explain as in depth as you can how you simplfied the fractions. i don't know where to start on this : /