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14x^2-14xy-8x+8y
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\(x^2-xy-8x+8y\)
\(=x\left(x-y\right)-8\left(x-y\right)=\left(x-8\right)\left(x-y\right)\)
Bài làm
8x2 - 12xy - 8y2 = 0
=> ( 8x2 - 8y2 ) - 12xy = 0
=> 8( x2 - y2 ) - 12xy = 0
=> 8( x - y )( x + y ) - 12xy = 0
=> 4[ 2( x - y )( x + y ) - 3xy ] = 0
= ( 7x2 + 14xy + y2 ) - 1
= ( 7x + y )2 - 1
= [(7x + y) + 1] [( 7x + y) - 1]
49.x^2 - 1 + 14xy + y^2
= (49.x^2 + 14xy + y^2) - 1
= (7x + y)^2 - 1
= (7x + y + 1)(7x + y - 1)
a
\(8x^3-\dfrac{1}{125}y^3\\ =\left(2x\right)^3-\left(\dfrac{1}{5}y\right)^3\\ =\left(2x-\dfrac{1}{5}y\right)\left[\left(2x\right)^2+2x.\dfrac{1}{5}y+\left(\dfrac{1}{5}y\right)^2\right]\\ =\left(2x-\dfrac{1}{5}y\right)\left(4x^2+\dfrac{2}{5}xy+\dfrac{1}{25}y^2\right)\)
b
\(-x^3+6x^2y-12xy^2+8y^3\\ =-\left(x^3-6x^2y+12xy^2-8y^3\right)\\ =-\left(x^3-3.2y.x^2+3.\left(2y\right)^2.x-\left(2y\right)^3\right)\\ =-\left(x-2y\right)^3\\ =-\left(x-2y\right)\left(x-2y\right)\left(x-2y\right)\)
a: 8x^3-1/125y^3
=(2x)^3-(1/5y)^3
=(2x-1/5y)(4x^2+2/5xy+1/25y^2)
b: =(2y-x)^3
a) \(=2y^3\left(x^2-16\right)=2y^3\left(x-4\right)\left(x+4\right)\)
b) \(=7y\left(x^2-2x+1\right)=7y\left(x-1\right)^2\)
c) \(=2x^2\left(x+5y\right)-y\left(x+5y\right)=\left(x+5y\right)\left(2x^2-y\right)\)
a: \(2x^2y^3-32y^3=2y^3\left(x-4\right)\left(x+4\right)\)
b: \(7x^2y-14xy+7y=7y\left(x^2-2x+1\right)=7y\left(x-1\right)^2\)
\(a,=3\left(x-5\right)-x\left(x-5\right)=\left(3-x\right)\left(x-5\right)\\ b,=7\left(x^2-2xy+y^2\right)=7\left(x-y\right)^2\\ c,=\left(x^2+y^2-2xy\right)\left(x^2+y^2+2xy\right)=\left(x-y\right)^2\left(x+y\right)^2\\ d,=\left(y^2-6y+9\right)-25x^2=\left(y-3\right)^2-25x^2=\left(y-5x-3\right)\left(y+5x-3\right)\)
b) \(25-x^2+14xy-49y^2\)
\(=25-\left(x^2-14xy+49y^2\right)\)
\(=25-\left[x^2-2\cdot7y\cdot x+\left(7y\right)^2\right]\)
\(=25-\left(x-7y\right)^2\)
\(=5^2-\left(x-7y\right)^2\)
\(=\left[5-\left(x-7y\right)\right]\left[5+\left(x-7y\right)\right]\)
\(=\left(5-x+7y\right)\left(5+x-7y\right)\)
c) \(x^5+x^4+1\)
\(=x^5+x^4+1+x^3-x^3\)
\(=\left(x^5+x^4+x^3\right)+\left(1-x^3\right)\)
\(=x^3\left(x^2+x+1\right)+\left(1-x\right)\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left[x^3+\left(1-x\right)\right]\)
\(=\left(x^2+x+1\right)\left(x^3+1-x\right)\)
b: 25-x^2+14xy-49y^2
=25-(x-7y)^2
=(5-x+7y)(5+x-7y)
c: =x^5+x^4+x^3+1-x^3
=x^3(x^2+x+1)+(1-x)(x^2+x+1)
=(x^2+x+1)(x^3+1-x)
\(14x^2-14xy-8x+8y=14x\left(x-y\right)-8\left(x-y\right)=\left(x-y\right)\left(14x-8\right)\)
\(14x^2-14xy-8x+8y\)
\(=14x\left(x-y\right)-8\left(x-y\right)\)
\(=\left(14x-8\right)\left(x-y\right)\)
\(=2\left(7x-4\right)\left(x-y\right)\)