Khai triển: a) ( x^2+ 2y) ^3

a) x2+2y3=x23+3  .  x22  .  2y+3  .  x2  .  2y2+2y3

=x6+3  .  x4  .  2y+3  .  x2  .  4y2+8y3

= x⁶ + 6x⁴y + 12x²y² + 8y³;