Assume the length X in minutes of a particular type of telephone conversation is a random variable with probability density function f(x){1ke−ek, x>0
0,elsewhere
(a) Determine the value of k.
(b) Find the mean and standard deviation of X.

In a quadratic function of the form ax^2+bx+c, which of the following is not true? a. the y-intercept is c. b. if a is positive, the parabola opens up. c. the vertex has an x-coordinate of -b/2a. d. the axis of symmetry is the line y=-b/2a.