Răspuns :
1990^199 - 1989× 1990^198 = 1990^198 × (1990^1 - 1989) =1990^198 × ( 1990 - 1989) = 1990^198 × 1 = 1990^198
1990la puterea199 - 1989× 1990la puterea1998 = 1990la puterea199 × (1990la puterea1 - 1989) =1990la puterea 199 × ( 1990 - 1989) = 1990la puterea198 × 1 = 1990la puterea198 cred ca este bine