Răspuns:
17. (5x+y-1)(5x+y+1)-(5x+y) =
(5x+y)^2 -1-5x-y =
25x^2 +10xy+y^2 -1-5x-y.
18. (2V2+V3)^2 -(2V2-V3)^2 =
8+4V6+3-(8-4V6+3) =
8+4V6+3-(11-4V6) =
8+4V6+3-11-4V6 =
0+8V6 =
8V6.
EVERGREEN
