Question

Answer 1

1, 

a, \(\left(\dfrac{1}{2}x-3\right)^3=\left(\dfrac{1}{2}x\right)^3-3\left(\dfrac{1}{2}x\right)^2.3+\dfrac{3.1}{2}x.3^2-3^3\)

\(=\dfrac{1}{8}x^3-\dfrac{9}{4}x^2+\dfrac{27}{2}x-27\)

b, \(\left(2x^2+3y\right)^3=\left(2x^2\right)^3+3.\left(2x^2\right)^2.3y+3.2x^2.\left(3y\right)^2+\left(3y\right)^3\)

\(=8x^6+36x^4y+54x^2y^2+27y^3\)

2, a, \(x^3+12x^2+48x+64=\left(x+4\right)^3\)

Với x = 6 => \(\left(6+4\right)^3=10000\)

b, \(x^3-6x^2+12x-8=\left(x-2\right)^2\)

Với x = 22 => \(\left(22-2\right)^2=400\)

3, a, \(=x^3+27-54-x^3=-27\)

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