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!
a, (2y-1)^3
= \(\left(2y\right)^3-3.\left(2y\right)^2+3.2y.1^2-1^2\)
= \(8y^3-12y^2+6y-1\)
b, (3x^2 + 2y)^3
= \(\left(3x^2\right)^3+3.\left(3x^2\right)^2.2y+3.3x^2.\left(2y\right)^2+\left(2y\right)^3\)
= \(27x^6+54x^4y+36x^2y^2+8y^3\)
c, ( 1/3x - 2)^3
= \(\left(\dfrac{1}{3}x\right)^3-3.\left(\dfrac{1}{3}x\right)^2.2+3.\dfrac{1}{3}x.2^2-2^3\)
= \(\dfrac{1}{27}x^3-\dfrac{2}{3}x^2+4x-8\)
a, ( 2y - 1 )3 =(2y)3 - 3.(2y)2 .1 + 3.2y.12 - 13 = 8y3 -12y2 + 6y - 1
b,(3x2 + 2y)3 = (3x2)3 + 3.(3x2)2.2y + 3.3x2.(2y)2 + (2y)3 = 27x6 + 27x4 + 36x2y2 + 8y3
c,(\(\dfrac{1}{3}\)x - 2)3 = (\(\dfrac{1}{3}\)x)3 - 3.(\(\dfrac{1}{3}\)x)2.2 + 3.\(\dfrac{1}{3}\)x.22 -23 = \(\dfrac{1}{27}\)x3 - \(\dfrac{2}{3}\)x2 + 4x - 8
