Question

[kimtaeyeon]

Khai triển các hằng đẳng thức sau

1)(3x-2a)^3 2)(x+y/3)^3 3)(3x+y/3)^3 Giúp mk nha mk đang cần gấp

Answer 1

[qwerty]

1) \(\left(3x-2a\right)^3\)

\(=\left(3x\right)^3-3\left(3x\right)^2\cdot2a+3\cdot3x\cdot\left(2a\right)^2-\left(2a\right)^3\)

\(=27x^3-3\cdot9x^2\cdot2a+3\cdot3x\cdot4a^2-8a^3\)

\(=27x^3-54ax^2+36a^2x-8a^3\)

2) \(\left(\dfrac{x+y}{3}\right)^3\)

\(=\dfrac{\left(x+y\right)^3}{27}\)

\(=\dfrac{x^3+3x^2y+3xy^2+y^3}{27}\)

3) \(\left(3x+\dfrac{y}{3}\right)^3\)

\(=\dfrac{\left(3x+y\right)^3}{27}\)

\(=\dfrac{27x^3+27x^2y+9xy^2+y^3}{27}\)