Question

Khai triển các hằng đẳng thức sau:

a, \(\left(2x^3y-0,5x^2\right)^3\)

b, \(\left(x-3y\right)\left(x^2+3xy+9y^2\right)\)

c, \(\left(x^2-3\right).\left(x^4+3x^2+9\right)\)

Answer 1

a) \(\left(2x^3y-0,5x^2\right)^3\)

\(=\left(2x^3y\right)^3-3\left(2x^3y\right)^20,5x^2+3.2x^3y\left(0,5x^2\right)^2-\left(0,5x^2\right)^3\)

\(=8x^9y^3-6x^8y^2+1,5x^7y-0,125x^6\)

b) \(\left(x-3y\right)\left(x^2+3xy+9y^2\right)\)

\(=x^3-\left(3y\right)^3\)

\(=x^3-27y^3\)

c) \(\left(x^2-3\right)\left(x^4+3x^2+9\right)\)

\(=x^3-3^3\)

\(=x^3-27.\)