factorize x^2 + 4y^2 + 16z^2 + 4xy + 16yz + 8zx and find the value when x=2, y=-1 and z=1
x^2 + 4y^2 + 16z^2 + 4xy + 16yz + 8zx =, and it answers the first question. To answer the second questions, substitute the values into the right side of the formula. You will get = = = 16.