Question

Помогите с номерами 5 и 6
Дам 10 баллов

Answer 1

197² - 196² = (197- 196)(197 + 196) = 1 * 393 = 393

$\frac{68 ^{3} +17 ^{3} }{68+17} -68*17= \frac{(68+17)(68 ^{2}-68*17+17 ^{2} ) }{68+17} -68*17=68 ^{2} -68*17+$$17 ^{2} -68*17=68 ^{2}-2*68*17+17 ^{2}=(68-17) ^{2}=51 ^{2}=2 601$