Final answer:
The likelihood function is obtained by multiplying the values of the common pdf at each data point. The log-likelihood function is obtained by taking the natural logarithm of the likelihood function.
Step-by-step explanation:
The likelihood function is given by multiplying the values of the common pdf at each data point. In this case, the likelihood function is L(θ) = θx1 + x2 + ... + xne-2θne-20θ∑i=1nxi.
The log-likelihood function is obtained by taking the natural logarithm of the likelihood function. Therefore, the log-likelihood function is log L(θ) = (x1 + x2 + ... + xn)ln(θ) - 2nθ - 20θ∑i=1nxi.