There are 10 black and 5 white balls in a bag. Two balls are taken out, one after another, and the first ball is not placed back before the second is taken out. Assume that the drawing of each ball from the bag is equally likely. What is the probability that both the balls drawn are black?
Find the minimum value of ( z = x + 3y ) under the following constraints:
• x + y ≤ 8• 3x + 5y ≥ 15• x ≥ 0, y ≥ 0
Find the value of \[ \int \frac{\sec^2 2x}{(\cot x - \tan x)^2} \, dx. \]