Phân tích đa thức thành nhân tử
xy(x+y) + yz(y+z) +xz(x+z) + 2xyz
x2+5x+6
7x-6x2-2
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1) \(4x^2-7x-2=4x^2-8x+x-2=\left(4x^2-8x\right)+\left(x-2\right)\)
\(=4x\left(x-2\right)+\left(x-2\right)=\left(x-2\right)\left(4x+1\right)\)
2) \(4x^2+5x-6=4x^2+8x-3x-6=\left(4x^2+8x\right)-\left(3x+6\right)\)
\(=4x\left(x+2\right)-3\left(x+2\right)=\left(x+2\right)\left(4x-3\right)\)
3) \(5x^2-18x-8=5x^2-20x+2x-8=\left(5x^2-20x\right)+\left(2x-8\right)\)
\(=5x\left(x-4\right)+2\left(x-4\right)=\left(x-4\right)\left(5x+2\right)\)
4) \(xy\left(x+y\right)-yz\left(y+z\right)+xz\left(x-z\right)\)
\(=xy\left(x+y\right)-y^2z-yz^2+x^2z-xz^2\)
\(=xy\left(x+y\right)+\left(x^2z-y^2z\right)-\left(yz^2+xz^2\right)\)
\(=xy\left(x+y\right)+z\left(x^2-y^2\right)-z^2.\left(x+y\right)\)
\(=xy\left(x+y\right)+z\left(x-y\right)\left(x+y\right)-z^2\left(x+y\right)\)
\(=xy\left(x+y\right)+\left(zx-zy\right)\left(x+y\right)-z^2\left(x+y\right)\)
\(=\left(x+y\right)\left(xy+xz-yz-z^2\right)=\left(x+y\right).\left[x\left(y+z\right)-z\left(y+z\right)\right]\)
\(=\left(x+y\right)\left(y+z\right)\left(x-z\right)\)
1) 4x2 - 7x - 2 = 4x2 - 8x + x - 2 = 4x( x - 2 ) + ( x - 2 ) = ( x - 2 )( 4x + 1 )
2) 4x2 + 5x - 6 = 4x2 - 8x + 3x - 6 = 4x( x - 2 ) + 3( x - 2 ) = ( x - 2 )( 4x + 3 )
3) 5x2 - 18x - 8 = 5x2 - 20x + 2x - 8 = 5x( x - 4 ) + 2( x - 4 ) = ( x - 4 )( 5x + 2 )
4) xy( x + y ) - yz( y + z ) + xz( x - z )
= x2y + xy2 - y2z - yz2 + xz( x - z )
= ( x2y - yz2 ) + ( xy2 - y2z ) + xz( x - z )
= y( x2 - z2 ) + y2( x - z ) + xz( x - z )
= y( x - z )( x + z ) + y2( x - z ) + xz( x - z )
= ( x - z )[ y( x + z ) + y2 + xz ]
= ( x - z )( xy + yz + y2 + xz )
= ( x - z )[ ( xy + y2 ) + ( xz + yz ) ]
= ( x - z )[ y( x + y ) + z( x + y ) ]
= ( x - z )( x + y )( y + z )
5) xy( x + y ) + yz + xz( x + z ) + 2xyz ( đề có thiếu không vậy .-. )
xy(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z2)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
xy(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z²)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
xy(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z²)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
xy(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z²)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
xy(x + y) + yz(y + z) + xz(x + z) + 2xyz
= x 2 y + x y 2 + yz(y + z) + x 2 z + x z 2 + xyz + xyz
= ( x 2 y + x 2 z) + yz(y + z) + (x y 2 + xyz) + (x z 2 + xyz)
= x 2 (y + z) + yz(y + z) + xy(y+ z) + xz(y + z)
= (y + z)( x 2 + yz + xy + xz) = (y + z)[( x 2 + xy) + (xz + yz)]
= (y + z)[x(x + y) + z(x + y)] = (y + z)(x+ y)(x + z)
xy(x+y)+yz(y+z)+xz(x+z)+2xyz
= xy(x + y) + yz(y + z) + xyz + xz(x + z) + xyz
= xy(x + y) + yz(y + z + x) + xz(x + z + y)
= xy(x + y) + z(x + y + z)(y + x)
= (x + y)(xy + zx + zy + z2)
= (x + y)[x(y + z) + z(y + z)]
= (x + y)(y + z)(z + x)
x2 + 5x + 6
= x2 + 2x + 3x + 6
= x(x + 2) + 3(x + 2)
= (x + 2)(x + 3)
7x - 6x2 - 2
= - 6x2 + 7x - 2
= - 6x2 + 3x + 4x - 2
= - 3x(2x - 1) + 2(2x - 1)
= (2x - 1)(-3x + 2)
mk ko pit lm câu a, xl nhé
\(\text{a) }xy\left(x+y\right)+yz\left(y+z\right)+xz\left(x+z\right)+2xyz\\ \\=x^2y+xy^2+y^2z+yz^2+x^2z+xz^2+xyz+xyz\\ \\=\left(x^2y+xy^2+x^2z+xyz\right)+\left(xz^2+yz^2+y^2z+xyz\right)\\ \\=x\left(xy+y^2+xz+yz\right)+z\left(xz+yz+y^2+xy\right)\\ \\=\left(x+z\right)\left(xy+y^2+xz+yz\right)\\ =\left(x+z\right)\left[\left(xy+y^2\right)+\left(xz+yz\right)\right]\\=\left(x+z\right)\left[y\left(x+y\right)+z\left(x+y\right)\right]\\ \\=\left(x+z\right)\left(y+z\right)\left(x=y\right) \)
\(\text{b) }x^2+5x+6\\ \\ =x^2+2x+3x+6\\ \\=\left(x^2+2x\right)+\left(3x+6\right)\\ \\=x\left(x+2\right)+3\left(x+2\right)\\ \\=\left(x+2\right)\left(x+3\right)\)
\(\text{c) }7x-6x^2-2\\ \\ =3x+4x-6x^2-2\\ \\ =\left(3x-6x^2\right)-\left(2-4x\right)\\ \\ =3x\left(1-2x\right)+2\left(1-2x\right)\\ \\ =\left(3x+2\right)\left(1-2x\right)\)