Răspuns:
a) (x+1)(x-1) = x²-1² = x²-1
b) (x+2)(x-2) = x²-2² = x²-4
c) (x+3)(x-3) = x²-3² = x²-9
d) (x+5)(x-5) = x²-5² = x²-25
==EVERGREEN==
