Завдання:
Якою цифрою закінчується значення виразу: 41 ⋅ 42 ⋅ 43 ⋅ 45 – 52 ⋅ 53 ⋅ 54 ⋅ 57?
Розв'язок:
Число 41 ⋅ 42 ⋅ 43 ⋅ 45 закінчується цифрою 0, а число 52 ⋅ 53 ⋅ 54 ⋅ 57 – цифрою 8.
Оскільки 52 ⋅ 53 ⋅ 54 ⋅ 57 > 41 ⋅ 42 ⋅ 43 ⋅ 45, то 41 ⋅ 42 ⋅ 43 ⋅ 45 – 52 ⋅ 53 ⋅ 54 ⋅ 57 = -(52 ⋅ 53 ⋅ 54 ⋅ 57 – 41 ⋅ 42 ⋅ 43 ⋅ 45) = -…8.
Відповідь: 8.