Note that the quadratic formula has that "plus or minus" due to our taking the square root of some quantity. No square root is involved in the two formulas you've posed.
I have two suggestions here:
1) Write " (x plus or minus y)^2 = x^ plus or minus 2 times xy + y^2 " Note that a + on the left side corresponds to a + on the right side, and same with - .
2) Memorize these two formulas, which in most algebra textbooks you'll find in the section "special products and factoring."
