Răspuns :
( 4 - 11 + 8 ) ·√11 - ( 7 - 9 ) ·√11 + ( 15 - 18)·√11 =
= 1·√11 - ( - 2) ·√11 + ( -3) ·√11
= ( 1 + 2 - 3) ·√11 = 0 ·√11 = 0
= 1·√11 - ( - 2) ·√11 + ( -3) ·√11
= ( 1 + 2 - 3) ·√11 = 0 ·√11 = 0