I do not understand this

Which expression is rational? 6. , square root two, square root 14, square root 49

Benefit(s) from large economies of scale, in which the costs of goods decrease as output increases. natural monopolles perfect competition

Use the given information to determine the exact trig value. cot theta = -square root of 5 / 2 , pi/2 < theta < pi, tan theta a.) - square root of 5 / 5 c.) - 2 square root of 5 / 5 b.) - square root of 5 / 2 d.) the answer isn't d, it was incorrect