A+b=16 ab=-28 a^(3)+b^(3)=?

Question

A+b=16 ab=-28 a^(3)+b^(3)=?

Answer 1

(a+b)^3=16^3
a^3+3a^2b+3ab^2+b^3=4096
a^3+b^3=4096-3ab(a+b)
a^3+b^3=4096-448
a^3+b^3=3648

Answer 2

A+b=16    ab=-28      a³+b³=?
(a+b)²=a²+2ab+b²=16²=256
a²-ab+3ab+b²=256
a²-ab+b²=256-3ab
a²-ab+b²=256-3*(-28)=256+84=340
a³+b³=(a+b)(a²-ab+b²)=16*340=5440.