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1. 4-32x3
= 4.(1-8x3)
= 4.[13-(2x)3 ]
= 4.(1-2x).(1+2x+4x2)
2. b. \(\left(\frac{x}{xy-y^2}-\frac{2x-y}{xy-x^2}\right):\left(\frac{1}{x}+\frac{1}{y}\right)\)
\(=\left[\frac{x}{y\left(x-y\right)}+\frac{2x-y}{x\left(x-y\right)}\right]:\left(\frac{y}{xy}+\frac{x}{xy}\right)\)
\(=\left[\frac{x.x}{y\left(x-y\right).x}+\frac{\left(2x-y\right).y}{x\left(x-y\right).y}\right]:\left(\frac{x+y}{xy}\right)\)
\(=\left[\frac{x^2+2xy-y^2}{xy\left(x-y\right)}\right]:\left(\frac{x+y}{xy}\right)\)
\(=\left[\frac{-\left(x-y\right)^2}{xy\left(x-y\right)}\right].\frac{xy}{x+y}\)
\(=\frac{-\left(x-y\right)}{xy}.\frac{xy}{x+y}\)
\(=\frac{y-x}{x+y}\)
\(y\left(x-y\right)^2+xy\left(x-y\right)\)
\(=\left(xy-y^2\right)\left(x-y\right)+xy\left(x-y\right)\)
\(=\left(xy-y^2+xy\right)\left(x-y\right)\)
\(=\left(2xy-y^2\right)\left(x-y\right)\)
y ( x - y)2 + xy ( x-y) = (x - y) [(x-y) y +xy]
= (x-y) ( 2xy -y2)
a) xy(x + y) + yz(y + z) + xz(z + x) + 3xyz
= xy(X + y + z) + yz(x + y + z) + xz(X + y + z)
= (x + y +z)(xy + yz+ xz)
b) xy(x + y) - yz(y + z) - xz(z - x)
= x2y + xy2 - y2z - yz2 - xz2 + x2z
= x2(y + z) - yz(y + z) + x(y2 - z2)
= x2(y + z) - yz(y + z) + x(y + z)(y - z)
= (y + z)(x2 - yz + xy - xz)
= (y + z)[x(x + y) - z(x + y)]
= (y + z)(x + y)(x - z)
c) x(y2 - z2) + y(z2 - x2) + z(x2 - y2)
= x(y - z)(y + z) + yz2 - yx2 + x2z - y2z
= x(y - z)(y + z) - yz(y - z) - x2(y - z)
= (y - z)((xy + xz - yz - x2)
= (y - z)[x(y - x) - z(y - x)]
= (y - z)(x - z)(y -x)
phần 1 đề nhầm ak sửu lại nha:
\(\left(8x^3+1\right):\left(4x^2-2x+1\right)=\left(2x+1\right)\left(4x^2-2x+1\right):\left(4x^2-2x+1\right)=2x+1\)
2) \(x^2-y^2-6x+6y\)
\(=\left(x-y\right)\left(x+y\right)-6\left(x-y\right)\)
\(=\left(x-y\right)\left(x+y-6\right)\)
a) x(y - x)3 + y(x - y)2 + xy(x - y)
= x(y - x).(y - x)2 + y(x - y)2 + xy(x - y)
= x(y - x)(x - y)2 + y(x - y)2 + xy(x - y)
= (x - y)[x(y - x)(x - y) + y(x - y) + xy]
= (x - y)[x(y - x)(x - y) + y(x - y) + xy]
b) 3a2x - 3a2y + abx - aby
= 3a2(x - y) + ab(x - y)
= a(x - y)(3a + b)
a) x( y - x )3 - y( x - y )2 + xy( x - y )
= -x( x - y )3 - y( x - y )2 + xy( x - y )
= ( x - y )[ -x( x - y )2 - y( x - y ) + xy ]
= ( x - y )[ -x( x2 - 2xy + y2 ) - yx + y2 + xy ]
= ( x - y )( -x3 + 2x2y - xy2 - yx + y2 + xy )
= ( x - y )( -x3 + 2x2y - xy2 + y2 )
b) 3a2x - 3a2y + abx - aby
= 3a2( x - y ) + ab( x - y )
= ( x - y )( 3a2 + ab )
= ( x - y )a( 3a + b )
Đặt x^2+y^2+z^2 =a ; xy+yz+zx=b
=> (x+y+z)^2 =x^2+y^2+z^2+2xy+2yz+2zx =a+2b
Ta có A= (x^2+y^2+z^2)(xy+yz+zx) +(x+y+z)^2
= a(a+2b)+b^2=a^2+2ab+b^2=(a+b)^2
=(x^2+y^2+z^2 +xy+yz+zx)^2
TL:
\(\left(x-y\right)\left(x^2+xy+y^2\right)\)
\(=x^3+x^2y+xy^2-yx^2-xy^2-y^3\)
\(=x^3-y^3\)
\(\left(x-y\right)\left(x^2+xy+y^2\right)\)
\(=x\left(x^2+xy+y^2\right)-y\left(x^2+xy+y^2\right)\)
\(=\left(x^3+x^2y+xy^2\right)-\left(x^2y+xy^2+y^3\right)\)
\(=x^3+x^2y+xy^2-x^2y-xy^2-y^3\)
\(=x^3-y^3\)