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a)
\(4x^2-9y^2+6x-9y=\left(2x-3y\right)\left(2x+3\right)+3\left(2x-3y\right)\)
\(=\left(2x-3y\right)\left(2x+3y+3\right)\)
b)
\(1-2x+2yz+x^2-y^2-z^2=\left(x^2-2x+1\right)-\left(y^2-2yz+z^2\right)\) (đổi dấu)
\(=\left(x-1\right)^2-\left(y-z\right)^2\)
c)
\(x^3-1+5x^2-5+3x-3=\left(x-1\right)\left(x^2+x+1\right)+5\left(x-1\right)\left(x+1\right)+3\left(x-1\right)\)
\(=\left(x-1\right)\left(x^2+x+1+5\left(x+1\right)+3\right)\)
\(=\left(x-1\right)\left(x^2+x+1+5x+5+3\right)\)
\(=\left(x-1\right)\left(x^2+6x+9\right)=\left(x-1\right)\left(x+3\right)^2\)
a) 5x3 - 40 = 5( x3 - 8 ) = 5( x - 2 )( x2 + 2x + 4 )
b) x2z + 4xyz + 4y2z = z( x2 + 4xy + 4y2 ) = z( x + 2y )2
c) 4x2 - y2 - 6x + 3y = ( 4x2 - y2 ) - ( 6x - 3y ) = ( 2x - y )( 2x + y ) - 3( 2x - y ) = ( 2x - y )( 2x + y - 3 )
d) x2 + 2x - 4y2 + 1 = ( x2 + 2x + 1 ) - 4y2 = ( x + 1 )2 - ( 2y )2 = ( x - 2y + 1 )( x + 2y + 1 )
e) 3x2 - 3y2 - 12x + 12y = 3( x2 - y2 - 4x + 4y ) = 3[ ( x2 - y2 ) - ( 4x - 4y ) ] = 3[ ( x - y )( x + y ) - 4( x - y ) ] = 3( x - y )( x + y - 4 )
f) x3 + 5x2 + 4x + 20 = x2( x + 5 ) + 4( x + 5 ) = ( x + 5 )( x2 + 4 )
g) x3 - x2 - 25x + 25 = x2( x - 1 ) - 25( x - 1 ) = ( x - 1 )( x2 - 25 ) = ( x - 1 )( x - 5 )( x + 5 )
a) \(5x^3-40=5\left(x^3-8\right)=5\left(x-2\right)\left(x^2+2x+4\right)\)
b) \(x^2z+4xyz+4y^2z=z\left(x^2+4xy+4y^2\right)=z\left(x+2y\right)^2\)
c) \(4x^2-y^2-6x+3y=\left(4x^2-y^2\right)-\left(6x-3y\right)\)
\(=\left(2x-y\right)\left(2x+y\right)-3\left(2x-y\right)=\left(2x-y\right)\left(2x+y-3\right)\)
d) \(x^2+2x-4y^2+1=x^2+2x+1-4y^2\)
\(=\left(x+1\right)^2-4y^2=\left(x+2y+1\right)\left(x-2y+1\right)\)
e) \(3x^2-3y^2-12x+12y=3\left(x^2-y^2-4x+4y\right)\)
\(=3\left[\left(x^2-y^2\right)-\left(4x-4y\right)\right]=3\left[\left(x-y\right)\left(x+y\right)-4\left(x-y\right)\right]\)
\(=3\left(x-y\right)\left(x+y+4\right)\)
f) \(x^3+5x^2+4x+20=\left(x^3+5x^2\right)+\left(4x+20\right)\)
\(=x^2.\left(x+5\right)+4\left(x+5\right)=\left(x^2+4\right)\left(x+5\right)\)
g) \(x^3-x^2-25x+25=\left(x^3-x^2\right)-\left(25x-25\right)\)
\(=x^2\left(x-1\right)-25\left(x-1\right)=\left(x-1\right)\left(x^2-25\right)\)
\(=\left(x-1\right)\left(x-5\right)\left(x+5\right)\)
a)5x2y-10xy2
=5xy(x-2y)
b,:4x(2y-z)+7y(z-2y)
=4x(2y-z)-7y(2y-z)
=(2y-z)(4x-7y)
c,:y(x-z)+7(z-x)
=y(x-z)-7(x-z)
=(x-z)(y-7)
d)36-12x+x^2
=x2-2.x.6+62
=(x-6)2
e) (x-5)^2-16
=(x-5)2-42
=(x-5-4)(x-5+4)
=(x-9)(x-1)
f) 8x^3+1/27
=(2x)3+(1/3)3
=(2x+1/3)(4x2+2/3.x+1/9)
Bài làm
a) 4x - 8y
<=> 4( x - 2y )
b) 12x( x - 2y ) - 8y( x - 2y )
<=> ( 12x - 8y )( x - 2y )
<=> 4( 3x - 2y )( x - 2y )
c) 2x + 2y - x2 - xy
= 2( x + y ) - x( x + y )
= ( x + y )( 2 - x )
d) x2 - 4y2
<=> ( x - 2y )( x + 2y )
e) x3 + x2y - 4x - 4y
<=> x2( x + y ) - 4( x + y )
<=> ( x - 2 )( x + 2 )( x + y )
g) 3x2 - 6xy + 3y2 - 12x3
<=>3( x2 - 3xy + y2 - 4x3 )
# Học tốt #
a)4(x-2y)
b)(x-2y)(12x-8y)
=4(x-2y)(3x-2y)
c)2(x+y)-x(x+y)
=(2-x)(x+y)
d)(x-2y)(x+2y)
e)x2(x+y)-4(x+y)
=(x+y)(x2-4)
=(x+y)(x-2)(x+2)
g)3(x2-2xy+y2-4z3)
=3[(x-y)2-4z3]
????????????phải là 4z2chứ nhỉ.....
a) x3 + x2y - x2z - xyz
= ( x3 + x2y ) - ( x2z + xyz )
= x2( x + y ) + xz( x + y )
= ( x + y )( x2 + xz )
= x( x + y )( x + z )
b) x2 - y2 + 6x + 9
= ( x2 + 6x + 9 ) - y2
= ( x + 3 )2 - y2
= ( x - y + 3 )( x + y + 3 )
c) x2 - 4xy - x + 2y + 4y2
= ( x2 - 4xy + 4y2 ) - ( x - 2y )
= ( x - 2y )2 - ( x - 2y )
= ( x - 2y )( x - 2y - 1 )
d) 18x3 - 12x2 + 3x - 2
= ( 18x3 - 12x2 ) + ( 3x - 2 )
= 6x2( 3x - 2 ) + ( 3x - 2 )
= ( 3x - 2 )( 6x2 + 1 )
e) a2 + 2ab + b2 - c2 + 2cd - d2
= ( a2 + 2ab + b2 ) - ( c2 - 2cd + d2 )
= ( a + b )2 - ( c - d )2
= ( a + b - c + d )( a + b + c - d )
f) xz - yz - x2 + 2xy - y2
= z( x - y ) - ( x2 - 2xy + y2 )
= z( x - y ) - ( x - y )2
= ( x - y )( z - x + y )
a) x3 + x2y - x2z - xyz
= ( x3 + x2y ) - ( x2z + xyz )
= x2( x + y ) + xz( x + y )
= ( x + y )( x2 + xz )
= x( x + y )( x + z )
b) x2 - y2 + 6x + 9
= ( x2 + 6x + 9 ) - y2
= ( x + 3 )2 - y2
= ( x - y + 3 )( x + y + 3 )
c) x2 - 4xy - x + 2y + 4y2
= ( x2 - 4xy + 4y2 ) - ( x - 2y )
= ( x - 2y )2 - ( x - 2y )
= ( x - 2y )( x - 2y - 1 )
d) 18x3 - 12x2 + 3x - 2
= ( 18x3 - 12x2 ) + ( 3x - 2 )
= 6x2( 3x - 2 ) + ( 3x - 2 )
= ( 3x - 2 )( 6x2 + 1 )
e) a2 + 2ab + b2 - c2 + 2cd - d2
= ( a2 + 2ab + b2 ) - ( c2 - 2cd + d2 )
= ( a + b )2 - ( c - d )2
= ( a + b - c + d )( a + b + c - d )
f) xz - yz - x2 + 2xy - y2
= z( x - y ) - ( x2 - 2xy + y2 )
= z( x - y ) - ( x - y )2
= ( x - y )( z - x + y )
a,\(\frac{1}{5}x^2y\left(15xy^2-5y+3xy\right)=3x^3y^3-x^2y^2+\frac{3}{5}x^3y^2\)
b,\(5x^3-5x=5x\left(x^2-1\right)=5x\left(x-1\right)\left(x+1\right)\)
c, \(3x^2+5y-3xy-5x=3x\left(x-y\right)-5\left(x-y\right)\)
\(=\left(3x-5\right)\left(x-y\right)\)
1) 1/5x2y( 15xy2 - 5y + 3xy ) = 3x3y3 - x2y2 + 3/5x3y2
2) a) 5x3 - 5x = 5x( x2 - 1 ) = 5x( x2 - 12 ) = 5x( x - 1 )( x + 1 )
b) 3x2 + 5y - 3xy - 5x = ( 3x2 - 3xy ) + ( 5y - 5x )
= 3x( x - y ) + 5( y - x )
= 3x( x - y ) + 5[ -( x - y ) ]
= 3x( x - y ) - 5( x - y )
= ( 3x - 5 )( x - y )
a,\(xy+3x-7y-21\)
\(=x\left(y+3\right)-7\left(y+3\right)\)
\(=\left(y+3\right)\left(x-7\right)\)
\(b,2xy-15-6x+5y\)
\(=\left(2xy-6x\right)+\left(-15+5y\right)\)
\(=2x\left(y-3\right)-5\left(3-y\right)\)
\(=2x\left(y-3\right)+5\left(y-3\right)\)
\(=\left(y-3\right)\left(2x+5\right)\)
a: =3x(4x^2-2x+1)
b: =(x+y)(x+4)
c: =(x-2y)(5x^2-15xy)
=5x(x-2y)(x-3y)