a) \(8x^3-y^3-6xy\left(2x-y\right)=\left(2x-y\right)\left(4x^2+2xy+y^2\right)-6xy\left(2x-y\right)\)
\(=\left(2x-y\right)\left(4x^2+2xy+y^2-6xy\right)=\left(2x-y\right)\left(4x^2-4xy+y^2\right)\)
\(=\left(2x-y\right)\left(2x-y\right)^2=\left(2x-y\right)^3\)
b) \(\left(3x+2\right)^2-2\left(x-1\right)\left(3x+2\right)+\left(x-1\right)^2\)
\(=\left[\left(3x+2\right)-\left(x-1\right)\right]^2=\left(3x+2-x+1\right)^2=\left(2x+3\right)^2\)
a) 8x3 - y3 - 6xy(2x - y)
= (2x)3 - y3 - 3.2x.y.(2x - y)
= (2x - y)3
b) (3x + 2)2 - 2(x - 1)(3x + 2) + (x - 1)2
= (3x + 2 - x + 1)2
= (2x + 3)2
Trả lời:
a, 8x3 - y3 - 6xy ( 2x - y )
= ( 2x - y )( 4x2 + 2xy + y2 ) - 6xy ( 2x - y )
= ( 2x - y )( 4x2 + 2xy + y2 - 6xy )
= ( 2x - y )( 4x2 - 4xy + y2 )
= ( 2x - y )( 2x - y )2
= ( 2x - y )3
b, ( 3x + 2 )2 - 2 ( x - 1 )( 3x + 2 ) + ( x - 1 )2
= [ ( 3x + 2 ) - ( x - 1 ) ]2
= ( 3x + 2 - x + 1 )2
= ( 2x + 3 )2
