Find a positive number x CALC HELP!?

To find the minimum of 2x + (1/2x) with a positive number x, take the derivative of 2x + (1/2x), which is 2 - (2)(1/(4x^2)) and make it equal to 0. Well, this simplifies to 2 - 1/(2x^2), which equals 0 when 2x^2 = 1/2, which happens when x = 0.5. So you are right.