Question

Tinh

a) ( y-3) . ( y +3)

b) \(\left(3n-2m\right)^3\)

Answer 1

a) ( y-3) . ( y +3) = y . (y + 3) - 3 . (y + 3) = y² + 3y - 3y - 9 = y² - 9

b) \(\left(3n-2m\right)^3=\left(3n\right)^3-3.\left(3n\right)^2.2m+3.3n.\left(2m\right)^2-\left(2m\right)^3=27n^3-54n^2m+36nm^2-8m^3\)

Answer 2

a) \(\left(y-3\right)\left(y+3\right)=y^2-9\)

b)  \(\left(3n-2m\right)^3=\left(3n\right)^3-3.\left(3n\right)^2.2m+3.3n.\left(2m\right)^2-\left(2m\right)^3\)

= \(27n^2-54n^2m+36nm^2-8m^3\)