\(a)\,{x^3} + 12{x^2} + 48{\rm{x}} + 64 \)\(= {{\rm{x}}^3} + 3.{{\rm{x}}^2}.4 + 3.x{.4^2} + {4^3} = {\left( {x + 4} \right)^3}\)
Với \(x = 6\) ta có: \({\left( {6 + 4} \right)^3} = {10^3} = 1000.\)
\(b)\,{x^3} - 6{{\rm{x}}^2} + 12{\rm{x}} - 8 \)\(= {x^3} - 3.{{\rm{x}}^2}.2 + 3.x{.2^2} - {2^3} = {\left( {x - 2} \right)^3}\)
Với \(x = 22\) ta có: \({\left( {22 - 2} \right)^3} = {20^3} = 8000.\)
