Problem 1) We need exactly one unit tile (the smallest square tile) to fill up the empty space to make a completed rectangle. In this case it would be (x+2)^2 = x^2+4x+4
Problem 2) The answer here is choice B since (x+3)^2 expands out to x^2+6x+9. Tacking on a "-6" will take the +9 down to +3. In other words, x^2+6x+9-6 = x^2+6x+3
