(1𝑦/3+3)^3

(𝑦/3+3)^3

(𝑦/3+3⋅3/3)^3

(𝑦+3⋅3/3)^3

(𝑦+9/3)^3

\(\left(\dfrac{1}{3}y+3\right)^3=\dfrac{1}{27}y^3+y^2+9y+27\)

\(\left(\dfrac{1}{3y+3}\right)^3=\dfrac{1}{\left(3y+3\right)^3}=\dfrac{1}{27y^3+81y^2+81y+27}\)

\(\left(\dfrac{1}{3y+3}\right)^3=\dfrac{1^3}{\left(3y+3\right)^3}=\dfrac{1}{27\left(y^3+3y^2+3y+1\right)}\)

a) \(\left(3x^2-2y^3\right)^2\)

\(=\left(3x^2\right)^2-2\cdot3x^2\cdot2y^3+\left(2y^3\right)^2\)

\(=9x^4-12x^2y^3+4y^6\)

b) \(\left(-2x^2-3\right)^2\)

\(=\left(-2x^2\right)^2-2\cdot\left(-2x^2\right)\cdot3+3^2\)

\(=4x^4+12x^2+9\)

a) \(\left(2x^2-1\right)^2=\left(2x^2\right)^2-2.2x^2.1+1^2\)

\(=4x^4-4x^2+1\).

b) \(\left(\frac{1}{2}x+3y^2\right)^2=\left(\frac{1}{2}x\right)^2+2.\frac{1}{2}x.3y^2+\left(3y^2\right)^2\)

\(=\frac{1}{4}x^2+3y^2x+9y^4\)

Chúc bn hc tốt!

a) \(12\left(2x-5\right)^2-3\left(1+4x\right)\left(4x-1\right)\)

\(=12\left[\left(2x\right)^2-2.2x.5+5^2\right]-3\left(4x+1\right)\left(4x-1\right)\)

\(=12\left(4x^2-20x+25\right)-3\left[\left(4x\right)^2-1\right]\)

\(=48x^2-240x+300-3\left(16x^2-1\right)\)

\(=48x^2-240x+300-48x^2+3\)

\(=-240x+303\)

A = (25+15).(25^2-15.25+15^2)/4 - 25.15

   = 40.475/4 - 375 = 10.475 - 375 = 4750 - 375 = 4375

k mk nha bạn ơi

a: Ta có: \(\left(x+y\right)^3-\left(x-y\right)^3\)

\(=x^3+3x^2y+3xy^2+y^3-x^3+3x^2y-3xy^2+y^3\)

\(=6x^2y+2y^3\)

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

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

\(=8y^3+6y\left(x^2-y^2\right)\)

\(=8y^3+6x^2y-6y^3\)

\(=2y^3+6x^2y\)

( A   –   B ) 3   =   ( A   +   ( - B ) ) 3       =   A 3   +   3 . A 2 . ( - B )   +   3 . A . ( - B ) 2   +   ( - B ) 3       =   A 3   –   3 A 2 B   +   3 A B 2   –   B 3     = >   ( A   –   B ) 3   =   A 3   –   3 A 2 B   –   3 A B 2   +   B 3

là sai

Đáp án cần chọn là: B