A teacher has four books—A, B, C, and D—to assign to four students in any order he prefers.
Set S includes all possible arrangements of the four books.
Set X includes all possible arrangements when book C is chosen first and D is chosen second.
Which notation is correct?
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If book C is chosen first and D is chosen second, in how many ways can the teacher assign the books?

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

Is there a direction u in which the rate of change of f(x,y)equals=x squared minus 3 xy plus 4 y squaredx2−3xy+4y2 at p(1,2) equals 14? give reasons for your answer. choose the correct answer below. a. no. the given rate of change is smaller than the minimum rate of change. b. no. the given rate of change is larger than the maximum rate of change. c. yes. the given rate of change is larger than the minimum rate of change and smaller than the maximum rate of change.

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test