a) \(\left(2y-1\right)^3\)\(=2y^3-3.\left(2y\right)^2.1+3.2y.1^2-1^3\)
\(=2y^3-12y^2+6y-1\)
b)\(\left(3x^2+2y\right)^3\)
\(=\left(3x^2\right)^3+3.\left(3x^2\right)^2.2y+3.3x^2.\left(2y\right)^2+\left(2y\right)^3\)
\(=27x^8+3.9x^4.2y+9x^2.4y+8y^3\)
\(=27x^8+54x^4y+36x^2y+8y^3\)
c)\(\left(\dfrac{1}{3}-2\right)^3\)
\(=\left(\dfrac{1}{3}x\right)^3-3.\left(\dfrac{1}{3}x\right)^2.2+3.\dfrac{1}{2}x.2^2-2^3\)
\(=\dfrac{1}{27}x^3-3.\dfrac{1}{9}x^2.2+x.2^2-8\)
\(=\dfrac{1}{27}x^3-\dfrac{2}{3}x^2+4x-8\)
Chúc bạn học tốt!
