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=x3(x+2)-13x2+12x-26x+24
=x3(x+2)-x(13x-12)-2(13x-12)
=x3(x+2)-(13x-12)(x+2)
=(x+2)(x3-x-12x+12)
(x+2)[(x2-1)-12(x-1)]
=(x+2)[x(x-1)(x+1)-12(x-1)]
=(x+2)(x-1)[x(x+1)-12]
=(x+2)(x-1)(x2+x-12)
=(x+2)(x-1)(x2-3x+4x-12)
=(x+2)(x-1)[x(x-3)+4(x+3)]
=(x+2)(x-1)(x-3)(x+4)
trong bài làm của mk có hàng k có dấu "=" chỗ đó có dâu"=" nha!
a) 3( x - y ) - 5x( y - x )
= 3( x - y ) - 5x[ -( x - y ) ]
= 3( x - y ) + 5x( x - y )
= ( 3 + 5x )( x - y )
b) x3 + 2x2y + xy2 - 9x
= x( x2 + 2xy + y2 - 9 )
= x[ ( x + y )2 - 32 ]
= x( x + y - 3 )( x + y + 3 )
c) 14x2y - 21xy2 + 28x2y2
= 7xy( 2x - 3y + 4xy )
Bài giải
\(a,\text{ }3\left(x-y\right)-5x\left(y-x\right)\)
\(=3\left(x-y\right)+5x\left(x-y\right)\)
\(=\left(x-y\right)\left(3+5x\right)\)
\(b,\text{ }x^3+2x^2y+xy^2-9x\)
\(=x\left(x^2+2xy+y^2-9\right)\)
\(=x\left[\left(x+y\right)^2-3^2\right]\)
\(=x\left(x+y+3\right)\left(x+y-3\right)\)
\(c,\text{ }14x^2y-21xy^2+28x^2y\)
\(=7xy\left(2x-3y+4x\right)\)
\(=7xy\left(6x-3y\right)\)
\(x^3-x^2-14x+24\)
\(=x^3-2x^2+x^2-2x-12x+24\)
\(=x^2\left(x-2\right)+x\left(x-2\right)-12\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+x-12\right)\)
\(=\left(x-2\right)\left(x^2+4x-3x-12\right)\)
\(=\left(x-2\right)\left[x\left(x+4\right)-3\left(x+4\right)\right]\)
\(=\left(x-2\right)\left(x+4\right)\left(x-3\right)\)
Ta có:\(x^3-x^2-14x+24=\left(x^3-2x^2\right)+\left(x^2-2x\right)-\left(12x-24\right)\)
\(=x^2\left(x-2\right)+x\left(x-2\right)-12\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+x-12\right)\)
\(=\left(x-2\right)\left(x^2-3x+4x-12\right)\)
\(=\left(x-2\right)\left[x\left(x-3\right)+4\left(x-3\right)\right]\)
\(=\left(x-2\right)\left(x+4\right)\left(x-3\right)\)
\(x^4-14x^2-7x+30=\left(x^4+x^3-3x^2\right)+\left(-x^3-x^2+3x\right)+\left(-10x^2-10x+30\right)\)
\(=x^2\left(x^2+x-3\right)-x\left(x^2+x-3\right)-10\left(x^2+x-3\right)\)
\(=\left(x^2+x-3\right)\left(x^2-x-10\right)\)
a/ Đa thức này không phân tích được thành nhân tử bạn nhé.
b/ $(x+y)(y+z)(x+z)+xyz$
$=xy(x+y)+yz(y+z)+xz(x+z)+2xyz+xyz$
$=[xy(x+y)+xyz]+[yz(y+z)+xyz]+[xz(x+z)+xyz]$
$=xy(x+y+z)+yz(x+y+z)+xz(x+y+z)=(x+y+z)(xy+yz+xz)$
c/
$x^8+x^7+1=(x^8-x^2)+(x^7-x)+x^2+x+1$
$=x^2(x^6-1)+x(x^6-1)+x^2+x+1$
$=(x^6-1)(x^2+x)+x^2+x+1$
$=(x^2+x+1)(x-1)(x^3+1)(x^2+x)+(x^2+x+1)$
$=(x^2+x+1)[(x-1)(x^3+1)(x^2+x)+1]=(x^2+x+1)(x^6-x^4+x^3-x+1)$