Question

1) (y+3t)(9t²-3yt+y²)

Answer 1

 

$\bullet$ `(y+3t)(9t^2-3yt+y^2)` `= (3t+y)(9y^2-3yt+y^2)` `= (3t)^3+y^3` `= 27t^3+y^3` $\bullet$ Áp dụng HĐT số `6:` `(A+B)(A^2-AB+B^2)=A^3+B^3`

Answer 2

(y + 3t)(9t² - 3yt + y²)

= (y + 3t)[(3t)² - 3yt + y²)]

= y³ + 3t³ 

=> 3t³ + y³