Question

D=(x+y)³-9(x+y)²+27(x+y)-27. Tại x=2, y=6

Answer 1

\(D=\left(2+6\right)^3-9\left(2+6\right)^2+27\left(2+6\right)-27\)

    \(=8^3-3\cdot3\cdot8^2+3\cdot3^2\cdot8-3^3\)

     \(\left(8-3\right)^3=5^3=125\)