Let x1, be a random sample from distributions with the given probability density functions. in each case, find the maximum likelihood estimator theta f(x; theta) = (1/theta2)xe-x/theta, 0 < x < infinity, 0 < theta < infinity. f(x; theta) = (l/2theta3)x2 e-x/theta, 0 < x < infinity, 0 < theta < infinity. f(x; theta) = (1/2)e- x- theta , -infinity