Using the definition of covariance, cov(x, y) = e[(x – my)(y – my)], prove the followings. a. cov(x, y) = e(xy) - mx hy b. cov(x, y) = cov(y, x) c. cov(x, x) = var(x) d. cov(x + z, y) = cov(x, y) + cov(z, y) e. cov(ex, y)= xcov(x, y) f. var(x + y) = var(x) + var(y) + 2cov(x, y) g. var(ex) = var(x) + ej cov(x, x; )

(least common multiples) the answer that i had in the 1st step was lcm of airline tickets sold=72. idk if that even matters but just in case. ! three co-workers are busy selling airline tickets over the phone. in an 8-hour day, charles can sell 8 airline tickets, ann can sell 9 airline tickets, and michelle can sell 6 airline tickets. step 2 of 2: what is the smallest number of 8-hour days needed for each of them to achieve the same number of sales? it takes charles . it takes . it takes .

Find the volume of the solid obtained by rotating the region enclosed by the curves y=1x and y=7^-x about the x-axis. (use symbolic notation and fractions where needed.) volume =

Through which points should a line of rotation be placed to create a cylinder with a radius of 3 units