Discover Questions

Have we proved Hebb's postulates? Is Earth the oldest planet in the Milky Way galaxy? Why does sqrt(4)-sqrt(16) not equal two? If sqrt(4) equals +-2 and sqrt(16) equals +-4, then could you not say -2+4 = 2? Simplified and completely factored form of of 12x + 4x + 25y + 15y? How would you prepare 300ml of a 0.6M solution from a 4M stock solution?