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a )
\(5x^2-10xy+5y^2-20z^2\)
\(=5\left(x^2-2xy+y^2-4z^2\right)\)
\(=5\left[\left(x-y\right)^2-4z^2\right]\)
b )
\(-5x^2-16x-3\)
\(=-5x^2-15x-x-3\)
\(=-5x\left(x+3\right)-\left(x+3\right)\)
\(=\left(-5x-1\right)\left(x+3\right)\)
c )
\(x^2-5x+5y-y^2\)
\(=\left(x^2-y^2\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left[\left(x+y\right)-5\right]\)
d )
\(3x^2-6xy+3y^2-12z^2\)
\(=3\left(x^2-2xy+y^2-4z^2\right)\)
\(=3\left[\left(x-y\right)^2-4z^2\right]\)
P/s : Mình bổ sung :
a )
\(=5\left(x-y-2z\right)\left(x-y+2z\right)\)
d )
\(=3\left(x-y-2z\right)\left(x-y+2z\right)\)
\(a,4x^4-8x^3+4x^2\)
\(=4x^2\cdot\left(x^2-2x+1\right)\)
\(=4x^2\cdot\left(x-1\right)^2\)
\(b,x^2-y^2+5\cdot\left(y-x\right)\)
\(=\left(x-y\right)\cdot\left(x+y\right)-5\cdot\left(x-y\right)\)
\(=\left(x-y\right)\cdot\left(x+y-5\right)\)
\(c,3x^2-6xy+3y^2-12z^2\)
\(=3\cdot\left(x^2-2xy+y^2-4x^2\right)\)
\(=3\cdot\left[\left(x-y\right)^2-\left(2x\right)^2\right]\)
\(=3\cdot\left(x-y-2x\right)\cdot\left(x-y+2x\right)\)
1, <=> \(\left(4x\right)^2-\left(9y\right)^2\)=\(\left(4x-9y\right)\left(4x+9y\right)\)
1) \(16x^2-81.y^2=\left(4x\right)^2-\left(9.y\right)^2=\left(4x-9y\right)\left(4x+9y\right)\)
2) \(\left(5x-3y\right)^2-\left(3x-5y\right)^2=\left(5x-3y-3x+5y\right)\left(5x-3y+3x-5y\right)=\left(2x+2y\right).\left(8x-8y\right)\)
\(=16.\left(x+y\right)\left(x-y\right)\)
3)\(4x^2-y^2+4y-4=4x^2-\left(y^2-4y+4\right)=\left(2x\right)^2-\left(y-2\right)^2=\left(2x-y+2\right).\left(2x+y-2\right)\)
4)\(9.\left(x-y\right)^2-16.\left(2x+y\right)^2=3^2.\left(x-y\right)^2-4^2.\left(2x+y\right)^2=\left(3x-3y\right)^2-\left(8x+4y\right)^2\)
\(=\left(3x-3y-8x-4y\right)\left(3x-3y+8x+4y\right)=\left(-5x-7y\right).\left(11x+y\right)\)
Phân tích các đa thức sau thành nhân tử :
a) x - y + 5x - 5y
= ( x + 5x ) - ( y + 5y )
= x . ( 1 + 6 ) - y . ( 1 + 6 )
= ( 1 + 6 ) . ( x - y )
\(a,x-y+5x-5y=\left(x-y\right)+5\left(x-y\right)=6\left(x-y\right)\)
a)x2-y2-5x+5y
=(x-y)(x+y)-5.(x-y)
=(x-y)(x+y-5)
b)5x3-5xy-10x2+10xy
=5x3+5xy-10x2
=5x.(x2+y-2x)
c)x3-3x2+1-3x
=x3+1-3x2-3x
=(x+1)(x2-x+1)-3x.(x+1)
=(x+1)(x2-x+1-3x)
=(x+1)(x2-4x+1)
d)3x2-6xy+3y2-12z2
=3.(x2-2xy+y2-4z2)
=3.[(x-y)2-4z2]
=3.(x-y-2z)(x-y+2z)
a) x3 - 4x2 + 4x - xy2
= x( x2 - 2.2x + 22 - y2)
= x[( x- 2)2 - y2]
= x( x -2 -y).(x - 2 +y)
b) x3 - 4x2 + 12x - 27
=( x3 - 33 )- 4x( x - 3)
= ( x - 3).( x2 + 3x + 9) - 4x( x-3)
= ( x-3).( x2 + 3x +9 -4x )
= ( x-3) .( x2 - x + 9)
c) 5x3 - 5x2y - 10x2 + 10xy
= 5x( x2 - xy - 2x + 2y)
= 5x[ x( x -y) - 2( x -y)]
= 5x.( x -2).( x -y)
d) 3x2 - 6xy + 3y2 - 12z2
= 3( x2 - 2xy + y2 - 4z2)
= 3.[ ( x -y)2 - ( 2z)2]
= 3.( x - y - 2z ).( x -y +2z)
