Let x and y be random variables of the continuous type having the joint p. d.f. f(x, y)=8xy

The graph below shows the amount of money left in the school’s desk fund, f, after d desks have been purchased. for each new desk that is purchased, by how much does the amount of money left in the school’s desk fund decrease?

Cot(90° − x) = 1 the value of x that satisfies this equation is °. a. 60 b. 135 c. 225 d. 315

How can writing phrases as algebraic expressions you solve problems?