Help proving angle use for theorem

If eh = hg and hg=16, find the diameter of k

What is the average rate of change for this function for the interval from x=2 to x=4 ?

Answer asap! show all work! find the number of complex roots, the possible number of real roots and the possible rational roots of the polynomial function. then, solve for all roots. x^3 + 2x^2 + 3x + 6 = 0