a+b=6 a^3+b^3=72 найдите ab

а^3 + b^3 = ( a + b )( a^2 - ab + b^2 ) a^3 + b^3 = 72 a + b = 6 72 = 6( a^2 - ab + b^2 ) a^2 - ab + b^2 = 72 : 6 a^2 - ab + b^2 = 12 a^2 + b^2 = ( a + b )^2 - 2ab a + b = 6 ( a + b )^2 = 36 a^2 - ab + b^2 = 36 - 2ab - ab = 36 - 3ab 36 - 3ab = 12 3ab = 36 - 12 3ab = 24 ab = 8 Ответ 8