Hello everybody,

I am tackling the following problem relating to the regression intercept estimator:

"(a) Show that the least squares estimator

(b) Using the result of part (a), or otherwise, derive the variance of ".

My progress is very limited. On part (a), I cannot see how this is true. Given , I cannot equate the formula given to what it should be. It seems the formula given amounts to and I am short of an . I am willing to accept I may have made a mistake but I can't see it and this is a major concern.