3 Which property can be used to expand the expression

Enter the number of complex zeros for the polynomial function f(x) = x 4+ 5x² +6

Which one ? is the answer and how to find this answer

20 sharpened pencils are placed in a box containing an unknown number of unsharpened pencils suppose 15 pencils are removed at random and five of the remove pencils are sharpened based on this is it reasonable to assume that the number of unsharpened pencil is 40 explain your reasoning