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a.2x2y-6xy2
=2xy(x-3y)
b.3x(x-1)+7x2(x-1)
=(x-1)(3x+7x2)
c.3x(x-a)+5a(a-x)
=3x(x-a)-5a(x-a)
=(x-a)(3x-5a)
d.x2+6xy+y2
=(x-y)2
e.125x3+y6
=(5x)3+(y2)3
=(5x+y2)(10x2-5xy+y4)
f.5x2y-10xyz+5xz2
=5x(y2-2yz+z2)
=5x(y-z)2
g.x2-2xy+y2-x2+yz
=(x-y)2-x2+yz
=(x-y-x)(x-y+x)+yz
h.x2-x-6
=(x2)-2x-3x-6
=x(x-2)-3(x-2)
=(x-2)(x-3)
i.x4+4x2+5
=(x2)2+4x2+5
=(x2)2+4x2+2-2+5
=(x2+2)2-3
nhung bai nay de lam bn cu thay thua so chung la nhom thui, bn xem mk lam rui lam tip nhe
a) = 2xy(x - 3y)
b) = (x-1)(3x+7x2) = x(3+7x)(x-1)
c) = (x-a)(3x-5a) bn đổi + 5a(a-x) = -5a(x-a)
................................
a) x3-3x2+3x-1=0
⇔ ( x - 1 )\(^3\) = 0
⇔ x - 1 = 0
⇔ x = 1
b) 4x3-36x=0
⇔ 4x ( x\(^2\) - 9 ) = 0
⇔ 4x ( x - 3 ) ( x + 3 ) = 0
\(\Leftrightarrow\left[{}\begin{matrix}4x=0\\x-3=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=3\\x=-3\end{matrix}\right.\)
c) x6-1=0
⇔ x\(^6\) = 1
⇔ x = \(\pm\)1
d) x3-6x2+12x-8 = 0
⇔ ( x - 2 )\(^3\) = 0
⇔ x - 2 = 0
⇔ x = 2
C= (x2-10x+25)-4y2
= ( x - 5 )\(^2\) - 4y\(^2\) = ( x - 5 - 4y ) ( x - 5 + 4y )
E= x2-6xy+9y2 = ( x - 3y )\(^2\)
F=x3+6x2y+12xy2+8y3 = ( x + 2 )\(^3\)
G= x3-64 = ( x - 4 ) ( x\(^2\) + 4x +16 )
H= 125x3+y6 = ( 5x )\(^3\) + ( y\(^2\) )\(^3\) = ( 5x + y\(^2\) ) ( 25x\(^2\) - 5xy\(^2\) + y\(^4\) )
a) \(5ax-15ay+20a\)
\(=5a\left(x-3y+4\right)\)
b) \(6xy-12x-8y\)
\(=6\left(xy-2x-3y\right)\)
c) \(3ab\left(x-y\right)+3a\left(y-x\right)\)
\(=3a\left(x-y\right)\left(b-1\right)\)
d) \(x^2-xy+2x-2y\)
\(=\left(x+2\right)\left(x-y\right)\)
e) \(ax^2-5x^2-ax+5x+a-5\)
\(=\left(a-5\right)\left(x^2-x+1\right)\)
a, \(5ax-15ay+20a=5a\left(x-5y+4\right)\)
b, sai
c, \(3ab\left(x+y\right)+3a\left(y-x\right)=3ab\left(x+y\right)-3a\left(x+y\right)=\left(3ab-3a\right)\left(x+y\right)\)
d, \(x^2-xy+2x-2y=x\left(x+2\right)-y\left(x+2\right)=\left(x-y\right)\left(x+2\right)\)
Tượng tự ...
a) 5ax - 15ay + 20a = 5a( x - 3y + 4 )
b) 6xy - 12x - 8y = 2( xy - 6x - 4y )
c) 3ab( x - y ) + 3a( y - x ) = 3ab( x - y ) - 3a( x - y ) = ( x - y )( 3ab - 3a ) = 3a( x - y )( b - 1 )
d) x2 - xy + 2x - 2y = x( x - y ) + 2( x - y ) = ( x - y )( x + 2 )
e) ax2 - 5x2 - ax + 5x + a - 5 = x2( a - 5 ) - x( a - 5 ) + ( a - 5 ) = ( a - 5 )( x2 - x + 1 )
g) x2y - 4xy2 + 4y3 - 36yz2 = y( x2 - 4xy + 4y2 - 36z2 ) = y[ ( x2 - 4xy + 4y2 ) - 36z2 ] = y[ ( x - 2y )2 - ( 6z )2 ] = y( x - 2y - 6z )( x - 2y + 6z )
h) 4xy - x2 - 4y2 + m2 - 6m + 9
= ( m2 - 6x + 9 ) - ( x2 - 4xy + 4y2 )
= ( m - 3 )2 - ( x - 2y )2
= ( m - 3 - x + 2y )( m - 3 + x - 2y )
i) x2 + x - 12 = x3 - 3x + 4x - 12 = x( x - 3 ) + 4( x - 3 ) = ( x - 3 )( x + 4 )
k) 5x2 + 14x - 3 = 5x2 - x + 15x - 3 = x( 5x - 1 ) + 3( 5x - 1 ) = ( 5x - 1 )( x + 3 )
m) x2 - 5xy + 4y2 = x2 - xy - 4xy + 4y2 = x( x - y ) - 4y( x - y ) = ( x - y )( x - 4y ) < đã sửa đề >
n) 3x2 - 5xy + 2y2 + 4x - 4y = ( 3x2 - 5xy + 2y2 ) + ( 4x - 4y ) = ( 3x2 - 3xy - 2xy + 2y2 ) + 4( x - y ) = [ 3x( x - y ) - 2y( x - y ) ] + 4( x - y ) = ( x - y )( 3x - 2y ) + 4( x - y ) = ( x - y )( 3x - 2y + 4 )
f) 2x3 + 4x2y + 2xy2 = 2x( x2 + 2xy + y2 ) = 2x( x + y )2
mình k cho bạn rồi nha, tích lại cho mình, số điểm của mình là -159 điểm
Bài 1 :
a) 3x2 . ( 5x2 - 7x + 4 ) = 15x4 - 21x3 + 12x2
b) xy2 . ( 2x2y - 5xy + y ) = 2x3y3 - 5x2y3 + xy3
c) ( 2x2 - 5x ) . ( 3x2 - 2x + 1 ) = 6x4 - 4x3 + 2x2 - 15x3 + 10x2 - 5x
= 6x4 - 19x3 + 12x2 - 5x
d) ( x - 3y ) . ( 2xy + y2 + x ) = 2x2y + xy2 + x2 - 6xy2 - 3y3 - 3xy
Bài 2 :
a) A = x2 + 9y2 - 6xy
=> A = x2 - 2 . x . 3y + ( 3y )2
=> A = ( x - 3y )2
Thay x = 19 và y = 13 vào biểu thức A ta có :
A = ( 19 - 3 . 13 )2
=> A = ( 19 - 39 )2
=> A = ( -20 )2
=> A = 400
b) B = x3 - 6x2y + 12xy2 - 8y3
=> B = ( x - 2y )3
Thay x = 12 và y = -4 vào biểu thức B ta có :
B = [ 12 - 2 . ( -4 ) ]3
=> B = ( 12 + 8 )3
=> B = 203
=> B = 8000
= -3y3 + 2x2y - 5xy2 + x2 - 3xy
a, 5x2 - 45x = 5x(x - 9)
b, 3x3y - 6x2y - 3xy3 - 6axy2 - 3a2xy + 3xy
= 3xy(x2 - 2x - y2 - 2ay - a2 + 1)
= 3xy[ (x2 - 2x + 1) - (a2 + 2ay + y2) ]
= 3xy[ (x - 1)2 - (a + y)2 ]
= 3xy(x - 1 + a + y)(x - 1 - a - y)
f, 3xy2 - 12xy + 12x
= 3x(y2 - 4y + 4)
= 3x(y - 2)2
g, 2x2 - 8x + 8
= 2(x2 - 4x + 4)
= 2(x - 2)2
h, 5x3 + 10x2y + 5xy2
= 5x( x2 + 2xy + y2 )
= 5x(x + y)2
k, x2 + 4x - 2xy - 4y + y2
= (x2 - 2xy + y2) + (4x - 4y)
= (x - y)2 + 4(x - y)
= (x - y)(x - y + 4)
i, x3 + ax2 - 4a - 4x
= (x3 - 4x) + (ax2 - 4a)
= x(x2 - 4) + a(x2 - 4)
= (x + a)(x2 - 4)
= (x + a)(x + 2)(x - 2)
Chúc bạn học tốt !
\(l,=5x\left(y^2-2yz+5z\right)\\ m,=\left(x+1\right)^3-27y^3\\ =\left(x+1-3y\right)\left(x^2+2x+1+3xy+3y+9y^2\right)\\ n,=\left(x-3y\right)^2\\ o,=\left(x+2y\right)^3\\ p,=\left(5x+y^2\right)\left(25x^2-5xy^2+y^4\right)\\ q,=\left(x+2y\right)^2-2\left(x-2y\right)+1\\ =\left(x+2y-1\right)^2\)