CLICK ON THE PROBLEMS THEMSELVES FOR HINTS/HELP, CLICK ON THE "(Solution)" FOR THE ANSWER AND COMPLETE SOLUTION
#1 Expand x^2 - 144 (Solution)
#2 Find the difference between 9^2 and 4^2 without using a calculator (Solution)
#3 Expand 9a^2 - 49b^2 (Solution)
#4 Find the difference between 205^2 and 204^2 without using a calculator (Solution)
[CHALLENGE] Expand 4x^2 + 9 (Solution)